Intel can probably make faster stuff than they currently do but then their customers (PC manufacturers for instance) would have to modify all their stuff as well and they don't want to, or at least, won't want the same thing.
The real explanation is Intel has been complacent and lazy. We had 5 generations of the same chip. Enough is enough.
This is a crucial point. It's a coordination problem.
Drivers only need to be made for those components that Apple choose for their system vs the multitude combinations of GPU boards, drive systems, motherboard chips, wifi etc etc. that exist for a modern PC.
There's no steering committee for PCs (at least none that could be incorruptible by Intel) that could cause this change to happen industry wide. And there's been little appetite (yet) for Windows/Linux + ARM for consumer PCs to help this happen from the bottom-up.
Couldn't they remove obsolete instructions from the ISA & then emulate removed instructions? Sure, it would be slower than having them still in the ISA, but given software using them was written for older machines, it might wash out in the end.
Didn’t work out so well