That's why it was the perfect MLG game. Every shooter these days is more and more complex.
OTOH there is Counter-Strike which turns 20 this year and is the third most popular game on Steam right now. Most of the changes to the core game since ~2001 have been about balance as opposed to adding new mechanics.
Someone who played the game over a decade ago could pick it up today and still play on mostly the same game on mostly the same maps:
de_cache 2011
de_dust2: 2001
de_inferno: 1999
de_mirage: 2004
de_nuke: 1999
de_overpass: 2013
de_train: 1999
for some reason valve doesn't release new versions of the game but instead chooses to radically change all aspects of the game and call it counterstrike(increment code+1)
i like the model, much better than call of duty randomly naming things differently even though the games are fundamentally the same with a fresh coat of graphics on top
I know you probably don't care about things like movement accel curves or hitbox sizes (which have changed drastically over the years) but just look at the deagle, possibly the most iconic weapon of the franchise. the weapon went largely unchanged between 1.6 and source, but is almost unrecognizable in csgo. you simply can't use it the same way you could in the older games; it has a completely different role.
The fight for asymmetry is what makes the game fun.