I mean I found 46 different cassettes in 16 models for 9 speed on one of the most popular distributors for bike parts in the U.S. Certainly not as many as back in the late 90s early 2000s when 9 speed was new and still really high quality stuff but enough to keep my two current 9 speed bikes going without a problem and without resorting to Tourney level crap. I will note some of that is Linkglide compatible stuff but there is enough to keep rolling just fine and probably a good deal of NOS stuff if you need a super high end set up.

I think a big part of less parts is the pandemic hit everyone hard so making 10 different levels of old stuff that is not common anymore doesn't make as much sense for many of these manufacturers who are trying to save some money and cut down and some SKUs so they can keep in profitability as they recover from the pandemic which seems like so long ago but it wasn't a light switch but more like a big complicated turn on procedure that takes a really long time to get going fully.