What are you going to do instead? I am very close to moving from a 20-year-old GMail address to a custom domain and was planning to use Proton as the email host.
I was in your shoes a few years ago. Just move already. Don't worry about it. Get your own domain and point the MX records at literally any email service out there. If you don't like it you can just switch later. Just start using your own domain as soon as possible.
It really is life changing. When you have your own domain switching email services is risk free since your addresses don't change. You can literally try out all the email services out there.
For the record I'm a happy Proton customer. They seem to be the only ones who still care about PGP. I even interacted with them here on HN a few times.
I've been reasonably happy with Runbox. Decent features, pricing, and servers in Norway. The webmail isn't great, but I don't really use it. If you must have encryption, I think the only option is Tuta.
Proton. There are some other good alternatives. But since the rest of the family was also using Fastmail, I needed a solution that was user-friendly enough. Besides that, Proton Drive also made it possible to finally move away from our Dropbox Family subscription.
I' migrated to purelymail.com around 2 years ago and. Reaaally cheap, easy to set up and without any bloat whatsoever. The webpage might look sketchy at first, but don't judge a book by its cover :)
Sending an email from catch-all covered email is not a big issues also, create use, delete and it still works.
I am slowly transitioning to icloud from gmail, was thinking of proton but reading the above comment made me change my mind, good custom domain support is a must for me.
I have a catch-all and can reply from any address I please. If I reply from an email sent to retailer@mydomain.com it even auto populates the "from" address for me with "retailer", or I can choose to reply from one of my named accounts. It's really slick.
I think the big downside for a lot of people is that it's hosted in the USA where the government is definitely headed in an autocratic direction that is abusive of most countries who don't comply to rantings from an orange madman. Definitely a huge downside.