The "shills" are not wrong. Every single currency that ever existed went to zero. The USD will be no exception. Honestly, BTC will be no exception either.
I can pay my non-imaginary taxes with dollars. All my other bills also helpfully accept dollars. This gives dollars a useful non-imaginary quality crypto does not have.
There's a handful of objectively valuable things like air, water, and food which I literally cannot live without. The value of pretty much anything else is imaginary because it's subjective.
The value of cryptocurrency is just far more imaginary than dollars, euros, or even gold.
You can believe that phone bills are a purely imaginary human construct that has no physical meaning and your phone will still stop working when you stop paying them.
At some point these things we conjure up out of our collective imagination are every bit as real as the ground hitting you if you jump off a building.
Well, the USD is backed by the "full faith and credit of the United States government" which, however you may feel about it, isn't imaginary. Each dollar is a claim to a piece of output of the world's largest economy with the strongest military.