I'm interested in a reduced feature phone for myself, strictly to reduce pressure from every bank, pharmacy, clothing store, and supermarket to install their apps. So long as it runs Ankidroid and syncs via CardDav, I'd like a phone with as few features as possible.

The problem is that _my_ two important features are different from _your_ two important features. Almost by definition, no reduced feature phone would be fit for a large audience, unless that large audience has a single common denominator. Like with this Kosher Phone and it's religious target demographic.