Agreed. The current formula is outdated.
For instance, It was based on an aviation industry that featured a lot more air taxi (commuter turboprops) which actually added to the complexity factor because of fleet mix.
Those have since been replaced with bigger regional jets which count as air carriers which actually lower the traffic count index at a lot of Core 30 airports.
Worth also mentioning that high performance jets that fly under a November callsign also count the same as a C172 flying under a November callsign.
The way the contract is currently written, a radar controller sequencing 5 November-tailed jets with 5 November-tailed props on final, counts the same as sequencing 10 jets alone or 10 props alone, even though there's more complexity in blending the two. For towers, there's also no consideration for ground control, call for releases, vehicle operations on active runways, TMU coordination, etc. even though they all add to varying complexity of towers.
But to be honest, if we actually had a truthful and *fair* way of analyzing facility ratings, people would absolutely hate it. It's much easier for people to accept the illusion that N90's Islip area deserves the same pay as Newark area, and a busy as shit VFR tower is the same difficulty as a sleepy level 7 up/down.