I don't think this season has exposed the need for renewal. It's just shown what happens when 10 years worth of injuries happen in 6 months.
Virgil is a colossus of a player in the Paolo Maldini mould (who played for Milan until he was 41). If he wasn't taken out by Pickford trying one of the Cobra Kai moves he'd watched on Netflix, then Virgil continues his form and durability this season and for many years to come. He is not past his peak at 29 - far from it.
Similarly with Henderson - he's got better with age, not worse. He runs more, covers more, and presses more than probably most players in the league. His desire and dedication could see him in our midfield until he's 35, perhaps dropping deeper in a 'quarterback' role as Gerrard did.
Wijnaldum is almost never injured, is consistent, and does the hard yards week in, week out. If he stays, he could easily play until he's 35.
Salah is the league's top scorer, has lost none of his pace, and scores outrageous goals for fun.
Mane is indestructible and a force of nature. He's lost none of his pace or strength, and this is his first drop in form since that dazzling goal on his debut.
So whilst I'd agree we need to be mindful of not letting too many players grow old together without renewal, I don't think it's fair to say players are past their peak when there's no indication they can't stay at the top level for several years yet. Any perceived drop in form or physicality must be viewed in context of the wider injuries and other factors this season - not as a sign players are past it. Without Jota we've not been able to rest the front 3 often. Without Fabinho and Henderson in midfeld (and Thiago out for 3 months), we had to ask Gini to play every game to hold it all together. Without Virgil and Gomez, we play Trent and Robertson every week so we have some stability either side of our CB's. It's no wonder they're all a little tired.
Fabinho, Keita and Ox were intended as the successors to Henderson and Wijnaldum, but two are inconsistent and injury prone, and one is our emergency centre back.
As for Milner, Matip, Adrian, etc - they're obviously in a different bracket and none of them will likely be here in 2-3 years, unless we can rebuild Matip's body.
Without the injuries I think we retain the league this season, sign a few players in the summer, sell off some fringe players like Origi and Shaqiri, and we go again.
As it stands, a large truck has run over our squad, and whilst there's no doubt the team are tired after the last few seasons, I don't think that would be as big a factor with everyone fit and a full stadium. It's not just the big injuries that have hurt us - it's the inability to get players like Keita and Ox on the pitch for more than a few games, and Origi and Shaqiri's inability to step up consistently.
It will be interesting to see what Klopp and Edwards have lined up this summer, but we mustn't forget that we have younger players in Trent, Robertson, Gomez, Jones, and Jota who are not at their peak years yet, and I don't think as many of the others are as past it as the OP suggests.