Varsity high-school player, and I've seen little discussion of what I'm personally certain is the big change causing all of this (including the surge in pickleball)

It's the rackets -- partly because they're ultra-light, but mostly because of how ridiculously grippy the strings are, meaning you can put absurd spin on the ball.

Meaning, a ton more control from the baseline. This effectively renders net-play most of the time dangerous and impossible. You'll notice, no one goes to the net anymore. It's basically full-scale ping-pong now.

Hence, pickleball for regular people, because they'd like to do that.