This is called a monopoly. I know people who run their own mail servers to be as independent as possible. Ironically, they show up as spam in Gmail all the time because "This message is similar to messages that were identified as spam in the past." Meanwhile, it's a fucking simple one paragraph message to a programming mailing list. They have to wrestle with DMARK or choose not to as they feel DMARK is playing into the hands of the monopolies giving them too much influence and power over something as simple and fundamental as email.
If you’re not capable of setting up DMARC correctly then it’s a safe assumption you aren’t capable of adequately securing your email server. Which is even easier to mess up with much higher consequences. Even if you are not intending to be a spammer, if your server gets pwned you will become an unwitting one.
I set up my orgs SPF/DKIM/DMARC (we self host, they have feelings about corporate data sovereignity...) it look about 30 min having never touched them before, and maybe another 15 to write an ansible playbook to rotate the keys.
We do have a _tremendous_ amount of spam fail these checks, as well as a few legitimate organizations.... Some of our peer companies have sent out notices that they will bounce anything that fail these checks in the coming years, and we're probably going to to do the same before too long.
