Here's Lemmy's reply from yesterday triggered by the same concern:

https://lemmy.world/post/53735981

Gmail was actually the easiest one to separate from, if you just count the transferring email addresses. It is a pain in the ass because so many services fight like hell to hold onto your google account you sometimes have to jump through hoops to remove it--a security risk in itself.

The big sticking point for me so far is photos... there are other options, but itś all integrated into my phone in weird ways I don't want to bother with right now.