As for the Beatles, lets start with the "In your face" Reference you made-
If you compare the early Beatles over all "loud mixed songs" to that of
Nirvana, well, it's pretty much the same effect.
Meaning, both bands brought THAT "balls to the walls guitar grunge" to the
mainstream pop radio (their respective era's) ...which the masses responded
to quickly.
Granted, the songs must be good as well (obviously), but they both were
similar in that they were very aggressive for pop radio.

Also, I recall the Beatles were the first band (?) to really push the bass
upfront --which was another bold mixing strategy. (See the Abbey Road
Journals)

NOT a big fan of compression! NOT a big fan of reverb, as I think the 1980's
(pick any song mixed) used enough reverb for all of us and then some.

Personally, I find the mixing process to liberating. It's the only part of
the entire process (from writing the song, tracking, mixing and mastering)
that set's the creative part of you free. Of course, allot of post
production happens during the mix time too, but I think mixing is honestly
the most rewarding part -for me. That IS the time you actually get to paint
on the canvas.

Scott