Source: I work in finance.
1) they offer services for free or for a low cost (compared to "normal" banks)
2) when these services work, they do work
3) when - for whatever reasons - these services do not work their assistance/support is either not-existing or unreachable, and when (if) you manage to contact them they provide no solutions/fixes and more likely than not you end up with your account frozen or closed (with no actual idea of the reasons why it was frozen/closed)
Surely there must be something (in EU) that complicates matters (anti-money laundering Laws/limits to transfers/National and EU Authorities/whatever) but right now it seems to me like none of them is actually reliable (if it is used as secundary or tertiary card/means of payment they are fine but I wouldn't trust any of them as "primary".
BTW - just for the record - right now N26 has been ordered to suspend making new accounts in Italy by the Bank of Italy (since March 2022) assertedly due to not full compliance with anti-money laundering checks:
I've never been in a situation where a next-day SEPA transfer wasn't good enough though.