This works for grocery shopping and so, but not so much for last-minute online transfers. You would need to physically move to your bank office every time you need to move money between bank accounts.

If I need one day such app, probably I would use one of my bank, not a third party one.

I think the issue is that many (most?) bank apps in the EU will simply refuse to work if your Android phone runs some custom firmware and/or lacks Google Play Services, as a "security measure". Until not so long ago, my bank's 2FA app crashed just because I was using a non-standard keyboard app.... (now it shows a big red warning, but at least it doesn't crash).