Not many ways you can convert crypto into money if the banks aren't in on it, or allowed to be in on it.

But for every other use of ethereum it is definitely harder to block, not that there are very many other uses right now.

And EU could just block those NFT trading websites, making it all annoying enough to use that most non-super enthusiasts wouldn't bother, because while you cannot completely block something, you have effectively succeeded if the vast majority of your population cannot be bothered.