none of the major providers will deliver your email without your mail server having first built a reputation
There are definitely major, and easily-abusable “features” being implemented by the major email providers, but I don’t think your statement is correct. I have a Hetzner server, and I can receive email from it (to Gmail) just fine, as long as I have SPF, DMARC, and DKIM set up. I can also create a new server with a new IP and not have any issues. The issues may arise with shared IPs/ranges that are also being used by spammers. Otherwise, if you’re planning to send bulk email you just need to warm up the IP.
I agree. When leaving reddit I weighed my choices between setting up a forum or a lemmy community/instance and ultimately chose a forum due to their software being more polished & feature-rich, and the fact that threads can have long-term discussions. I really dislike the time-based nature of reddit & lemmy for many things.
I petitioned the forum software devs to join the fediverse though. It’s nice to see some of them already joining.