Thanks !
Well regarding Facebook, it was easy to take the decision of deleting it : I wasn’t using Facebook at all, not even Messenger. I did have an Instagram account tied to my Facebook account, but I was using it less and less. I think ultimately this is what drove my decision : aside from WhatsApp, I wasn’t using any other Meta service.
I feel like part of increasing one’s security is properly discarding one’s account when they’re not using it anymore.
Regarding Microsoft and Google on the other end : you’re right. Actually, I was planning to wait a little to make sure I didn’t forget anything. I have tweaked all options for both to increase privacy, and archived all emails locally so I can delete them from their web service.
The only thing that bothers me is you can only download a .pst archive with Microsoft. I think I saw a script on github to convert .pst to .eml but I haven’t looked into it further for now.
Once all of this is done, perhaps I’ll just keep these two accounts around for the few services that need them, although nuking them would feel cleaner. Peace of mind I guess.