

One is that I can keep family email (everyone on the server) in the same ecosystem, so private information send between family members isn’t as likely to leak.
Another is also privacy – my mail isn’t being used to build a profile about me.
I also like the control and the ability to look at logs. If I don’t get an email, I can look at the server and figure out why it didn’t show up. It just provides more information for me.
I’ve been running mail servers for about thirty years; my personal ones and production for 100K+ users.
The personal one is a pain for the reasons you mentioned. I use sendmail instead of postfix, but I was able to use some rules to push certain messages through other relays.
I signed up for Amazon SES and have so far stayed in their free tier. Mail coming from one of my addresses always goes through SES, and mail from any address to certain domains (aol.com, gmail.com, etc.) go through SES as well.
It allows me to ensure delivery for my important mails, but leave things up to chance for less important ones.
It’s the best solution I’ve been able to come up with for a really annoying situation. Big Tech ruined it all.