I think you've hit on exactly what's wrong with the modern shows, freightdawg...specially the fact that they are forever trying to, as you say, "push the limit". It's a symptom of decadence, of a society that has truly lost its way.

You're right that Mary Tyler Moore and Carol Burnett were the "gold standard" of comedy writing. There were a few really good shows back then. The Smother Brothers had a great show, for instance, but it didn't last long.

There's also a disease of political correctness hobbling all attempts at humor now. There are so many things that you cannot joke about at all anymore...because it might offend someone...and yet, note how extreme and offensive the humor IS now in a more general sense just of how it is presented. It's creepy.