I really didn’t have a hard time setting mine up and I’ve done it multiple times. Dovecot is a bit of a pain if you really want imap... but overall none of it is harder than most other things.
And this is precisely why I don’t think it’s worth it. I don’t want to have to worry that “most” domains will accept my mail, I want a big email service that has the clout to force domains to accept my mail. I shouldn’t have to solve the mystery of why my mail was rejected (or rather, why some provider thinks I’m sending spam). That’s why I do Fastmail.
I asked Fastmail support, and they basically said, "we're not really built for that." However, most of the other services I looked at had arduous terms (arbitration agreements), and even they were talking about delivery rates in ranges of 85-95%.
My takeaway has been that as an app creator, email is really unreliable, and I should try whenever possible not to make it a critical part of anything I build. If 5-10% of the people using your service can't get a password reset email, what do you do?
As someone without much experience with email of that nature, it doesn't seem like the major services actually solve the deliverability problem. If they have Google-style support where I can't get one of them on the phone if my emails aren't sending, then I might even be worse off using them rather than my own setup that I can at least debug and experiment with.