Bitcoin wanted to be the world's currency, with a techno goldbug understanding of what money is. That shades a lot of what we think of as crypto.
There are a lot of different versions of the idea though. A lot of variety exists in crypto now, and very little is deterministic. I don't want to rule out the positive possibilities, and outlawing is broad brush. The PCB grunted at crypto here. We can do
That said, the variety of possibilities also creates danger. Underregulated stable coins, for example, get very sketchy once you reach a certain size. If they keep growing, start embellished with dolaralized interest payments and such.... you now have a rogue banking system issuing its own US dollars. Good luck with that. The scale of fraud, and treacherously borderline fraud can be epic. I don't think we should downplay these.
OTOH, this is true of every part of the financial sector. Lets not pretend the current way the financial sector is structured isn't riddled with the kinds of problems crypto poses.
A country with some clever CB people, even a small one, should be bold and bring crypto into the pax. There's a lot you can do with a designed-4-a-purpose currency, and crypto is a very viable way to do many things. Bitcoin's origins, and much of crypto's present, is secrecy oriented. But, it's actually more natural to design a cryptocurrency for transparency. That's useful in a lot of circumstances.
Take time to understand wtf is going on and regulate, ban or encourage specific things for specific reasons. There's a lot to be gained, not just a lot to be lost. A properly regulated stable coin might be a great idea.
Keynes has made a comeback during the pandemic, and people are relearning war era ideas about controlling inflation. In that context and considering 2021's low interest rates, national savings bonds will probably soon be considered in various places. You don't need crypto to do this, but it does give you more flexibility in how you do it.