It is somewhat different because you need to convince other mail servers to cooperate with yours whereas the HTTPS server works directly with clients (browsers) and may function completely independently.

its not strange to me that is was done, just that you or anyone was attempting to do it, for their family no less, in the last 15 years.

Maybe I'm unlucky, but I get a pretty high volume of incoming spam on my mailserver. However about 99% of it originates from machines that are on essentially all the blacklists, so it's fairly easy to reject it in the SMTP session with a conservative DNSBL check, without getting into spamassassin-style content filtering (I also prefer rejecting in the SMTP session, because on the off chance that there was a false positive, the sender at least gets notified of the non-delivery, instead of their mail being silently eaten).

I agree that outgoing deliverability isn't really a problem for me either. I do have DKIM and SPF set up. I also am a fairly low-volume message source. I think self-hosting is more tricky if you're emitting large volumes of mail, like transactional emails for a business. But as a personal email server it's been fine for me.

Same. I never have any problems. There's even websites that will look at your domain to see if you end up on any blacklists, or if you have any public-facing misconfiguration. Easy to set it up once, and forget about it.