idk... the Euro was introduced in 1998/1999 I heard it was already pretty huge a couple of years later.

You're comparing a government mandated currency change vs grassroots currency.

That's not young at all. How much trouble did people have accepting Euro in 2011?

A government mandate certainly helps a currency develop.

Arguably scepticism towards the Euro as a currency and Britain wanting nothing to do with it after the crisis was a key pillar of Brexit, so I wouldn’t say it went down amazingly. I remember during the campaign there was a fairly widespread notion that an overly Europhile government like Tony Blair’s might irreversibly commit the UK to the Eurozone, which was always an act that polled terribly.

Nothing is on crypto payments because you never know how you are actually paying

There are stable coins as well, where you know exactly what you're paying.

Or that just the transfer fees would be more than most payments.

Or that no one would be able to properly use those payouts.