I stopped using almost everything, and I'm writing replacements for things I couldn't find replacements for, so yes, me too.
What do you use instead of Gmail?
I use german providers such as GMX and Tutanota.
Fastmail here
Protonmail for me.
If you don't mind me asking, what did you find useful enough to make it worthwhile to write one?
I'm working on a photos replacement (just the upload and share features) for me and my wife. It literally just uses s3 and some python to move photos around, nothing fancy.