It's decades and decades of the same theme: capitalism, technology, and globalization leading to selfishness and inequalities. An American perspective (but will tie in some British stuff);
1. Manufacturing shifts
One of the things you always hear politicians speak of (particularly in places with a manufacturing history) is "jobs coming back." "We need to create manufacturing jobs here." But the reality is, it's mostly just talk. The relentless drive for technological innovation to make as much profit as possible means a change in focus areas (places like the US and UK are known for its powerful services industry, financial industry, and tech). Combine that with globalization, and you have the opportunity to create the most efficient supply chain possible. Traditional "manufacturing" is replaced by more efficient automated manufacturing with a global chain. An Apple iPhone isn't made in an assembly line or a factory in California. It has design, tech, physical components (rare earths, gold, plastic, etc), assembly, testing, QA, sales, marketing, etc all around it. Apple will make it as efficient as possible to make profit for shareholders. The issue is, for maybe the first time, it's a very global process. When Henry Ford started manufacturing and selling cars, he didn't use a global supply chain. Apple today does. In 1900, something like 40% of Americans lived on farms. It's like 2% today. But those that moved away into cities, suburbs, etc became part of the industrialization and growth of America. However, when manufacturing became more efficient in the last several decades, it's not like all Americans went to work for banks or tech companies, because those companies knew how to utilize global resources. So what if you were in Flint Michigan when GM closed a plant? Well, if you have the skills, you can try to move into other high-end manufacturing or use functional skills (e.g. sales, marketing) to move industries. If you didn't, you very well could be left behind. Banks, Google, Apple, etc aren't spending decades training workers. They can get workers from abroad, and they need since many of them compete globally anyway. Manufacturing companies make things more efficient and global as they're also competing globally. America actually had 2x the manufacturing output n 2016 compared to 1984 but used 3x fewer workers.
You also have industries like paper that are in decline just because of the technological advancements and economics. Towns of thousands that relied on a paper mill may go into almost irreversible decline when the mills close. If you're part of that town, it's not like you can just pack up and move to New York or Silicon Valley.
2. Growth and Cuts
At the same time, a huge portion of the population benefits from growth and are willing to vote in politicians that cut taxes, public services, and the welfare programs (Reagan, Thatcher). This creates an absolute fight for resources and growth that continues for decades. "Haves" will want more and more while "Have Nots" have to made do with services that don't keep up with the times.
People didn't want to pay for services. During the growth phase, you have the "business-friendly" politician. Their goal is to bring jobs to the area, but often at the expense of long-term planning. If you're a mayor/governor for four years, it's much easier to underfund services (those that disproportionately impact the poor) while cutting taxes. You get hailed a genius job creator when you've actually done very little. Then, you can run for higher office. But all you're doing is leaving behind major issues for future politicians to solve. One day, you wake up, and you live in a city where there's a massive wealth gap, public transit is a mess, homeless population is on the rise, and the city/state has no money. The left-wing politician may get elected to solve this mess, but it's almost unsolvable because it's years and successive administrations' work (or lack of thereof) that caused this. It's a microcosm of a nation as a whole.
3. Taking Action (or Not)
Left-wing politicians talk about major changes needed. But they run into two problems:
1. Depending on where you are, the majority of people don't want massive changes. A 55-year old homeowner, for example, may like home prices skyrocketing as he/she can sell it and retire somewhere nice. They don't want massive tax rises, wealth taxes, etc or anything that could jeopardize their asset values.
2. Even in places where the population want major changes, left-wing politicians struggle to implement them as they're working on decades of the system that's in place. You can't solve all these issues in the short-term, but if you don't, people get angry. The right-wing then comes along and tells the public that the left-wing cannot govern.
Right-wing politicians understand this challenge. They are not advocating for the changes that left-wing politicians are. So their plans are the following:
1. Do nothing or cut taxes (tangible short-term benefit to those with assets)
2. Blame game (minorities, immigrants, illegal immigrants, foreign countries, etc)
Which of these political wings has it easier?
The right-wing in the UK had it down pat. They cut services and then turned around and blamed it on the EU/immigrants. They didn't say: "I want to cut the NHS." They said: "We love the NHS but we could have it run better if the EU didn't take all our money. British citizens first!" Easy message.
Short-term interests will trump long-term planning. Left-wing policies are focused on inclusivity (the right will respond and fuel culture wars) and longevity (Benefits of a $6 Trillion infrastructure bills don't show up on your next paycheck/tax bill immediately). So it's always fighting a losing cause. Even when they get into government, they cannot reverse decades of the trend of a system built on capitalism and globalization.
The Democrats have more leeway in America because the GOP is full-on off the deep end on social issues. So much so that they've lost suburban voters. America is also significantly more diverse than the UK (and many other countries), so the GOP's rhetoric doesn't go over well. In addition, the GOP don't even talk up things like healthcare. They talk about repealing Obamacare but not a replacement (which the Democrats used against them for their 2018 electoral success in the House). If the GOP was more willing to embrace minorities with conservative leanings and had actual healthcare policies over the years, I'd wager they would be more dominant like the Tories.
4. The People
In the end, as time goes one, people are selfish: a large chunk of the population don't like paying for things. They simultaneously want the government to take care of every problem while paying less and less in taxes. It means those that need government services the most get worse and worse services, but it doesn't impact the electorate enough (so far) for the mindset to shift.
Left-wing policies are often popular, but when it comes to actual implementation, it's way harder (particularly if the right wants to interfere). It only leads to a lot of delays, inefficiencies, etc, which only further emboldens the right to push to slash spending instead. There's also a degree of Nimbyism present, even among left-leaning voters, particularly in America. "Affordable housing and infrastructure spending sound good, but do it over there, not in my state/county/city/backyard." Ezra Klein had an article in the NY Times about liberal governing, and it's something that's just very hard among a difficult electorate. California governor Gavin Newsom pledged to build millions of houses in California but is way behind due to a variety of factors. Some of those may be that Democratic homeowners don't want to see a massive supply of homes in their neighborhood, only a small number of expensive homes, so that home prices are preserved. It's not like left-leaning people don't have their own selfish needs and wants.
Excerpt:
"When he ran for governor in 2018, Gavin Newsom promised the construction of 3.5 million housing units by 2025. Newsom won, but California has built fewer than 100,000 homes each year since.
Watching SB50, State Sen. Scott Wiener’s ambitious bill to allow dense construction near mass transit, fail has become an annual political ritual.
California talks a big game on climate change, but even with billions of dollars in federal funding, it couldn’t build high-speed rail between Los Angeles and San Francisco. The project was choked by pricey consultants, private land negotiations, endless environmental reviews, county governments suing the state government. It has been shrunk to a line connecting the midsize cities of Bakersfield and Merced, and even that is horribly over budget and behind schedule."
5. Rhetoric
Politicians know how hard it is to get things done, so they turn to blame rhetoric. At the same time, you get social media, echo chambers, and other sources that promote all kinds of rhetoric. It's easier for people to blame issues on others, outsiders, and the like, so these get popular. New-age politicians embrace these ideas to get a mass following. As a result:
-Congressmen that literally incited an insurrection are not only not punished but may actually be re-elected.
-Incompetent leaders that mishandled the pandemic actually gain in popularity.
Because actual solutions to everyday problems are hard, it's easier to convince the public through conspiracy theories and blame-game rhetoric. So much of American (and British) problems are created by Americans (or British) themselves, but it's much easier to blame foreigners/communists/global cabal led by the Rothschilds.
As SoS pointed out above, when the pandemic hit, it revealed the problems underlying in society:
-People struggled to collectively come together
-Politicians were too used to doing nothing but playing the blame game and were incapable of governing.
It shouldn't be a surprise. It's years and years in the making.