I've become very interested by the difference between modern popular music and that of decades gone by. The three main things that I've noticed is that older music tends to be more melodic generally, makes greater use of dynamic range, and has more complex rhythms.

One of the standouts to me is what you mentioned -- in older music, the bass often does heavy melodic lifting and in newer music, it tends to be mostly just carrying a beat.

Not saying one is "better" than the other -- that's a matter of taste. It's just interesting to note the change.

It's also interesting that if you ignore music after the '80s and just compare '80s to the decades before that, you could accurately say something very similar.

It also depends a lot on what musical genre we're talking about. Not all '80s music was new wave and the like.