Btw, crypto (like bitcoin) is only an alternative because of convention.
The complete history of bitcoins is globally trackable, and people could all decide that they'll pay more for bitcoins that came from Satoshi's initial hoard, or that they'll refuse to accept bitcoins that were ever seized by the FBI.
(Yes, there are mixers. But you'd just refuse to accept any bitcoin that took part in the mixer transaction, if any FBI coins were in there.)
Intentional mixers aren't even the half of it. You have large exchange operators that use a single wallet. They file KYC paperwork with governments, but that's not in the blockchain. From the perspective of the blockchain their whole exchange is one big mixer. A billion dollars goes in, a hundred was tainted, a billion dollars comes back out. The only information to trace which $100 that went in is the $100 that came back out isn't in the blockchain, it's in the exchange's private accounting database.
But if you propose to taint every coin that has ever passed through a major exchange, that's pretty much all of them.
All new ones. You can buy 'fresh coins' from miners directly.
You could also exempt some 'honourable' miners (ie a whitelist) from the taint.
All kinds of conventions are possible, depending on what people want to value.
The convention that all bitcoins are equally valuable is just that: a convention. And it's not even strictly adhered to, because some bitcoins are already more valuable than others.