In fairness, projectm is literally built on 90s tech (Winamp’s milkdrop).

For some reason around the early 00s peoples love for visualisations fell out of favour. Meanwhile clubs would still hire dedicated VJs and/or lighting guys so didn’t rely on math-based visualisations. Which meant fewer people contributing to developing cool new math.

Worse still, the few industries left that did care about beat detection were games like Guitar Hero, Beat Sabre and those dance machines in arcades; all of which were easier to have patterns programmed by a human due to the limited selection of songs on offer.