I’m going to say depth of field is the issue. In the 80’s and 90’s waterskiing was relatively hot and attracted a lot of guys in their 20’s. Lots of them/us were looking for a sport to do after high school or college. Skiing was relatively affordable and fun. Let’s go!
Flash forward a few years and those guys have improved and pushed each other. There are 160 skiers at Nats In M3 and it’s tough. You better be improving because your buddy sure is. Sport is getting more expensive but hey “I’m older and making a little more coin. It’s cool”.
Flash to the past 10 years. That group I described is now M5 ish. Competition is still tough even though everyone is older. Problem is that now the sport is on private lakes and never seen on TV or the news stand. Even if it was as soon as that young guy sees what the costs are he’s out. There are some, and good on ya, but it is not many.
There are a lot of great juniors. Some of them go on to be the pros putting up amazing scores in all events. Seems that most who don’t go that route burn out and drift away from the sport. When I think of the crew that hung with in M2-3 most picked up the sport later and stayed in for a long haul. That route is not happening near as much now. (All this is imho of course)