In a perfect world, your DNS server implementation would not allow, or at least require you to explicitly acknowledge, non-compliant configurations.
My years running Courier taught me this. I’m surprised that there are still 6,000 600 domains in the top million that are incorrectly configured without realizing it.
It is interesting mail is the only service to get its own explicit record type. Modern protocols like XMPP will use either SRV or TXT records.
MX was basically the first SRV record type, and then after that they went “we should really make a general case tool for this”.
It helps that mail predated DNS. DNS was standardised in 1983, SMTP (which wasn’t the first email protocol) was standardised in 1982.
Yes, modern services don’t get their own DNS RR, but plenty services have: