The ability to use standard protocols (IMAP and SMTP) is much more important to me than end-to-end encryption. I won't even touch an email service that doesn't support IMAP with a 10-foot pole no matter how secure they claim it is. I know some people are developing self-hosted gateways that can speak IMAP on the local side and a more secure protocol on the public side, and I think it shows promise. But the whole setup still feels way too fragile compared to good old email.
I've been using FastMail for 11 years now, and I've recommended it to several other people. I will continue to do so for the foreseeable future.
My work email has disabled imap in the name of security. My understanding is it's easier to lock down email entirely than to get doctors not to email patient data around, so I kind of understand, but it's annoying to have to read my email either using the terrible outlook web all or by giving my employer a lot of permissions on my personal phone. For context I'm in the US, where HIPAA fines can be quite high (not that that's a bad thing).
I've been using FastMail for 11 years now, and I've recommended it to several other people. I will continue to do so for the foreseeable future.