Yeah, SwiftUI is still immature in many areas, so each new version adds a lot of essential features. I'm not talking fancy new things, just the basic stuff that almost every app needs. The alternative is to implement through the older UIkit which is slower to do, especially for people like me who don't really know UIkit from before.
As for Avelon I'm using a few key features introduced with v16. Since I'm just one dev I prioritized polish and features over supporting older versions which would take much more time. Yeah, it sucks if you're stuck on iOS 15, but that's just what I decided to prioritize.
Ah ok, yeah that makes sense. I'll look at tweaking the touch target to make it easier to tap!