Take basic functionality - a phone app (calling). After certain audio sessions use (calling via WhatsApp) I can’t make regular calls over cellular - the UI app immediately cancels the call. Only reboot helps.
Or notes - for many years/iOS versions, they lived with a bug where a text note may just become blank - and only restarting Notes app makes it visible again.
Or AppStore - if an app has to be updated (I have auto updates off) - and I press Update - it gets downloaded, installed - and then AppStore is back to showing “Update” button! If you just go to the app, it’s a new version. But if you press that “Update”, it will redo update from scratch.
Sometimes I’m so frustrated, and thinking of my options - it’s either move to Android, or go get hired at Apple with a mandate to fix bugs in various products… but knowing Apple secrecy culture/silos, it’s not going to work, and requires change in their hiring process/perf review/QA.