Believe it or not, "apps" are an important "feature" of a smartphone, even if it's not theoretically bundled with it. Moreover it's not just banking apps, those are just the first ones to go, but any that don't keep backend compatibility will eventually break.
The entire point of the cellphone is that third party apps are required to live a modern life. If I cannot run the apps required to pay for a parking spot or perform a 2FA ritual then there’s really no point in even having a phone. The first party software isn’t compelling enough to justify the pocket space.
You could always keep your phone and get a second dirt-cheap phone just for the 2FA (or use your banks' non-phone 2FA methods). But if we take your requirement that one phone should be able to do everything that new phones can do, it's somewhat tautological that you have to replace your phone frequently to stay on the cutting edge.