If you look at "a single server for one person/organisation" some stuff have actually become simplier with apache > nginx > nginx or even LE.
If you tolerate docker deployment of some stuff has also become way easier. Same if you tolerate systemd.
On the other hand emails is not moving at all in that direction, quite the contrary...
I think nginx is a good example : it's easy for simple thing, like serving files or reverse-proxying some stuff. But more and more webapps needs complex server stacks for working, so the simplicity doesn't exists for a lot of things.
Then comes Docker. It hides complexity, not reduce it.
I've a ton of stuff where I pray it'll not crash, because if it does, I'll unable to repair it, not knowing the stack behind.
For mail, new tools more easy to configure are developped these days (OpenSMTPD for example). But there are no real world "simple stacks" for mail, like "simple file serving" in HTTP.
I'm not sure administrate a mail server is more complex than running most of modern web apps. But complexity of stack isn't hide by modern packaging tools.