You say that self-hosting a mail server is obvious and extremely low effort, which simply is not true. But ok, let's say that you happen to have a clean IP and no spam or dmarc issues. You still had to choose what to deploy, which is not obvious and actually setup/maintain your server which is not extremely low effort.
Please read the comment you are replying to again. I said that it's obvious that it's worth doing, not that the work to set it up is "obvious".
Of course you need to learn some things, but it's not that much work. If you're the type that enjoys learning this sort of thing, you'll have a good time. If you're not, don't do it!
