Tyres are and always will be a big issue in sims. They are probably the hardest of things to model correctly. Diffs, suspension etc are easy compared. Sure, LFS has issues on this area, a lot.
But what can you do? If you just simply increase the grip of hot tyres what will happen then? Wouldn't it it also be unrealistic if hot tyres would grip as almost well as optimal tyres? Solving the tyre problem is not easy like that. You need to rethink the whole issue not just some small part of it.
Again I am not saying that LFS tyres are perfect now, far from it. They are actually very simplistic now, only heat and the thickness of the rubber is taken in to account (afaik). In real life tyres have more attributes than that.
In conclusion tyres are a big issue. But do you think they should be the only issue? There are plenty of other things the devs have to also take care of. There is more to this than "this is wrong, now fix it".