So, let's say that Labour put into policy that doesn't support any of corporate-capitalist consensus or businesses in the UK as a whole. Completely gets rid of capitalism and entirely opposes all businesses across the board at every level - domestically and internationally.
What would be the economic result?
Well that's an extreme alternative, and it would - as you allude to - bring economic chaos.
An element of 'capitalism' is so deeply embedded in not just economies but in the psyche, that that must remain IMO. In fact, I believe a properly regulated version of capitalism is beneficial overall. One with strong workers' rights.
What we have, though, is corporations using their power to influence policy in their favour. And usually 'in their favour' is against the interests of 'the masses'.
I also agree with you and other that say Labour - or any left-leaning party - would struggle to get elected on a platform of outright radical-left economics. Left-leaning parties need to be smart in how they present manifesto pledges - but certainly not abandoning left-of-centre economic principles
That is a problem stemming from how the 'free press' is majority controlled by super-rich people with [at least economically] right-wing views - and they use their media outlets to influence voters into rejecting left-of-centre policies. When media are giving far-right/neo-nazi/fascist parties less criticism than an economically-progressive/mid-left party wanting proper regulation of business and finance and adequate levels of progressive taxation to fund strong public services, you know the whole media sphere is broken.
And we need to find a way to address the issue of housing and how prohibitively expensive it's become, especially for younger people trying to get on the ladder. The jeopardy, though, is not collapsing the market, which creates even more severe problems for existing home-owners. Most of the mammoth rise in prices has been driven by buy-to-let investors (low interest rates and sluggish stock markets have led the wealthy to seek new investment options that give a better RoI)
Finally, the issue of tax-dodging by the super-rich is massive and should be a priority for any even centrist government.
The difficult issue is, most of the problems require a collaboration between countries. I used to have a pipedream that the EU could become an economically progressive beacon, formulating bloc-wide policies to address proper regulation of business and finance and tax dodging. Sadly, I realised some time ago (prior to the Referendum) that the influence of the ECB was very strong and the ECB was stuffed with ex-Goldman Sachs corporate-capitalists who were intent on directioning the EU down that path (the aftermath of the GFC was brutal on countries like Greece, Italy, and others, with no fucks given for the hardships imposed on ordinary people). The EU is still a force for good and I'm gutted we're no longer part of it, but it isn't presently how I waqnt it to be.
[well, that was a rambling one!
)