Finally, a week ago, I switched my email to fastmail. Bought a new domain for 10 years explicitly for that purpose.
I'm slowly migrating everything to them... Every day or two I think of something else that needs to be migrated, and do it. I don't feel a need to rush because I just have them both simultaneously.
I have to say though, Fastmail feels better than Gmail in every way. The UI is fast and snappy, looks clean (with a few themes), includes a calendar and notes. The first month is free, so I figured I'd try it before I decided to go all in. After about 20 minutes I was sold and bought a year subscription...
They have this really cool feature with subdomain forwarding so you can organize things into folders automatically. As I've been migrating emails, I've been giving each service it's own unique email address. Eg `amazon@stores.domain.com` will automatically add the email to my "stores" folder, and I'll see it came from Amazon. I can put unlimited anything before the @ sign, which will be really nice for signing up for one-off forums. If they sell my email address or send spam, I'll know exactly who did it and can just block that address.
They also have a bunch of other features for organization like the "+ addressing" that Gmail has. I definitely recommend checking them out though. I feel so good having an email that won't get shut down