As a thought experiment, let's say someone invented a brilliant revolutionary new complex rhythm. Everyone went wild using it for a year. Then, once everyone knows it, artists start to mix it up by leaving out parts of it, leaving it implied, relying on listeners familiarity with the rhythm to make things work.

If you now tried to naively measure the amount of rhythmic complexity per song by counting percussion hits or similar, you'd see complexity take a nosedive. You'd also see people who missed out on the year complain about how bland the new rhythms are. But the songs actually got more complex. It's just that the complexity is only apparent to people familiar with the hypothetical revolutionary rhythm.

At the same time, people familiar with the new music will look back at the old music and be incredibly bored. They're used to finding enjoyment in the complexity of the implied rhythm, but there's just nothing there, it's all painfully spelled out and predictable.