For me it’s Whatsapp. Like 99% of people i know use it so yeh… i still need it. I am considering moving the Whatsapp Gdrive backup to a local backup btw.
Google photos is also a major problem for us. We have a lot of stuff that want to migrate to different service (or store locally).
The huge almost-unavoidable one is gmail. You might use a different email provider yourself, but whenever you email another person, there’s a high chance that they are a gmail user. So whatever you wrote lands on a gmail server and stays there forever. Someday the entire contents of those servers will be crunched through an AI to identify and round up the undesirables.
Other than that, I confess to using google maps for road navigation pretty regularly. I tried to switch to Organic Maps but it just doesn’t work anywhere near as well. Also I watch a lot of youtube, though without having an account on it.
I don’t use gdrive or whatever. I don’t have a google account. I switched from google photos to fossify gallery a while back but (mostly from laziness) I still haven’t degoogled a few of the other stock android apps, that hopefully don’t upload anything. And yeah, I’m still on android itself. I don’t use any google play apps though. Just f-droid.