Trying very hard to ignore this absolutely stupid take. But I can't.

Amethyst is objectively better in terms of security than all the other apps you mentioned, because it doesn't even need your keys to work. All of it's code is open source and built verifiably and signed by the dev. Which means you know that the app that is running on your phone is exactly the one that is coded by the dev.

Something that you can never ensure on apple. And apple apps have been known to almost certainly have Trojans. Read about cocoapods dependency injection.