It's not entirely a contradiction. De-Googled Android alternatives can give a perception of choice and also a perception to Banks that they support "everyone" at the same time. "We have both flavors, Vanilla (iOS) and Chocolate [Android]; you claim to want Chocolate (Android), what more do you want?"

Absolutely the current duopoly market is going to make any third-party alternative harder, but de-Googled Android seems to be a worst case because "Why not just install Google Play Services?" remains too valid a question and has too many confusing answers for both non-technical users and the business people at application providers (banks and whatnot). They will continue to have a hard time trying to figure out why you keep asking for a harder work effort for Chocolate Fudge when they already have Chocolate and why isn't that good enough.

It's easier to fix that confusion by asking for an entirely new brand/flavor, such as Strawberry, than continuing this increasingly hard war between Google's Chocolate and "free" (as in speech, but certainly not free of confusion) Chocolate Fudge.

There are tweaks to enable banking apps on deGoogled Android, but it's an exhausting cat and mouse game. Most of my friends gave up after years of fighting, and now they are back on Google Android because there is no alternative.