> “Tab to improve”. What I’ve written so far isn’t up to Gmail’s standards, it seems.

I find this infuriating. I have my own voice, my own writing style, and I deliberately use some "bad" writing tropes for effect. For any non-trivial amount of writing (read: anything with actual paragraphs), I'm liable to spend as much time editing as I am writing out the first draft, to make sure my writing conveys the message I want it to.

"Tab to improve" is, effectively, "tab to delete my own personality".

Somehow MS Word's grammar check does this without being offensive about it.