Actually, now that I look at it, Google Sheets doesn't pop your keyboard up when you tap on a cell. Once you deploy it you can leave it up, though, and it stays up even as you navigate around. TIL.
I believe it is capable of working offline. You are correct that Google by default really wants you to have everything on your Google Drive, though.
Complexity I'll grant you, but it's very cut down even compared to the desktop browser instance of Sheets. It's always been good enough for me, but hopefully some better versed Android nerds than me can come up with some alternatives for you. Now I'm curious to find out, too.
If you're fine with Google then Sheets has been alright for me. Does mostly everything I need. Doesn't pop up keyboard from a single tap on a cell but does for a double tap and keeps it up for subsequent fields.
I use OnlyOffice both for local device files and to connect to my nextcloud installation. Seems to have a fairly good feature set for docs, presentations and sheets!