I think that it's justified to treat cryptos for tax purposes the way fiat currencies are treated. Normally it means only income tax. In my country the legislation is tricky with two different ways and amounts to pay depending on the type of business. Anyway, there are countries with reasonable progressive tax system which even allows people with very small income not to pay anything.
There are also small states which are tax-free, and some zones for crypto businesses that allow not to pay taxes or not to pay a lot for a while.
The exchange idea is also nice. It's kind of like we all pay VAT which is embedded into the prices of goods. Easy and useful.
I'll never understand why people are so against giving what's due. I do agree and get in that tax in my home country is annoyingly unfair, since a lot of it ends up in corrupt hands. But it doesn't prevent me from paying my dues. You want to live in a country, enjoy the privileges and rights, and expect reasonable public services and amenities, then you have to do your part and support it.
I do like the idea of VAT too. Everything priced in. People in my country are all angry about it but come on, suck it up and pay for it. Or go find a tax free country. Or live off grid.