Anytime Mac or someone is listening to background music it’s always instrumental rock music , which I’ve never heard of before, clearly a composer had to insert it as part of the score of the episode.

Smart thinking back then so they didn’t have to get real music and pay licensing. A lot of shows back then weren’t as Careful because they weren’t thinking about syndication

I love the diegetic switch music from Jack of Lies.

And yeah these are very much in touch with the late 80s zeitgeist. I think. Some of this might be post fact. As in anything they did is late 80s, by definition. I'm not entirely sure.

for example, I know then TV shows used real canned music that was commercially released, it made DVD release impossible due to licensing. Macgyver was very lucky to not do that at all.

I think Michael Des Barres actually helped write the Cleo Rocks song

Got examples?

The wonder years, WKRP in Cincinnati

Also love the early 90s commuter sludge rock from Split Decision