This would be MASSIVE for me. I largely just write in a stream of consciousness and don’t pay any attention to spelling, punctuation or formatting. My phone keyboard, Word, OneNote, and most other writing applications that I’ve used all capitalize automatically, so the habit is deeply engrained.
If there could be a general Autocorrect feature (I don’t even capitalize proper nouns, for example) that would be an enormous improvement. Perhaps a separate feature request though? (I’ve opened one here)