I agree with you in practice, though there's no reason that it has to be this way. Email, like other protocols of its age, is simple. What's difficult is navigating the forest of roadblocks set up by the big email providers to excuse them not accepting your mail (or not sending their users' mail to you).
Most of these are alleged to have some purpose in preventing spam, but I think experience doesn't bear that out. They may prevent Joe jobs[1], and it may be reasonable to use the suspicion they create of a message being forged as one factor in deciding if a message is spam. But nothing really deals with spam except statistical analysis of messages.
The real point is that the major providers are anticompetative, and that's not really the fault of email as such.
Most of these are alleged to have some purpose in preventing spam, but I think experience doesn't bear that out. They may prevent Joe jobs[1], and it may be reasonable to use the suspicion they create of a message being forged as one factor in deciding if a message is spam. But nothing really deals with spam except statistical analysis of messages.
The real point is that the major providers are anticompetative, and that's not really the fault of email as such.
[1] https://en.wikipedia.org/wiki/Joe_job