The fact is that "wildly successful" today is against a background of reduced expectations. Thriller sold 70 million copies, Bat out of Hell (somehow) sold 43 million copies. That's on a different order of magnitude than what seems possible today.
I think part of what makes music interesting to listen to is the subtle imperfections and nonidealities. It hurts to listen to a pure sine wave but FM synthesis adds some richness, as does the three strings on a piano that are just slightly out of tune. Numerous artists that were productive and commercially successful in the 1970s failed to make a transition to the "music word processor" in the 1980s. They kept releasing albums but fans ignored them and will boo if they try to play anything but the old favorites. I think MIDI and the click track are part of the same problem as autotune... "Snap to grid" and a lot of what makes music interesting is just gone.