Fastmail for me, but yeah same. I did that a long time ago -- the only thing I use still is search and youtube. The latter of which has no real replacement sadly
I also use Kagi and I really enjoy it (enough to pay for the ultimate subscription), but it's hard for me to recommend to someone wanting to "degoogle" their life. Kagi search results depend (probably a lot) on the Google search API. If Google rug pulled that, Kagi search results would definitely be effected.
Not the parent, but also degoogled as much as pragmatic lately.
For files and photos, I use an NAS in my home (Synology). Works pretty smooth with automated photo backup etc. For office stuff I just use Libre Office, I don't need collaboration features. Not interested in cloud options personally, so sorry if that's not helpful. I'd probably go for Dropbox for most of this if I was.
Google Maps is, for me, unfortunately one of the services I wasn't able to replace yet. I tried to use OSM (also for navigating), which actually worked great for me. But I use satellite view so often (mostly for entertainment) that I couldn't quite break the Maps habit.
I don't use Proton but don't they offer a calendar and file storage? I know a lot of email providers do (I use mailbox.org and they do). Personally I host Nextcloud on a VPS and use that for file storage, calendar and photos.
Maps is a tough one. It's probably the main Google service I still use (YouTube being another one). There is OSM of course but it can't compete with Google on features.
Docs can be handled locally or via any other online office suite. Files can be stored anywhere, from local NAS to other remote storage services, Calendar is easily exported and imported somwhere else or locally. And maps can be used without account so you don't really need to export anything.