I've been using GrapheneOS for years and that hasn't been my experience. There are two financial apps that don't work for me, and that's it. Pretty much everything else I use is fine. But, to be fair, I'm very scrupulous about my apps and tend to avoid installing an app for every little thing that wants me to.
Sometimes, all you need is a Web browser. I personally don't want any "apps" on my phone that aren't basic utilities.
I am aware some banks in Europe require 2FA on a mobile device. Short of switching banks, my answer to that is a cheap or e-waste Googled Android phone that stays at home and serves that sole purpose.
Some banks limit functionality on web apps, which is annoying.
More importantly, many refuse to provide a decent 2FA other than push notifications inside the app or SMS, which is insecure and EU has mandated its phaseout.
The thing that works for me is to pretend to be clueless and get an old hardware OTP generator, but those are susceptible to impersonation attacks on the bank side.
I also need to maintain my own nextcloud, photo sync infrastructure and backups.
Its inconvinient. This is exactly what I talking about.
They probably use E2EE just so they don't have to respond to court orders and such.