Theoretically that's how it should work, but it gets to a point where it just doesn't get that much more challenging. Like there's some sort of wall, I guess? The best way I can describe it is with an older game: Quake 3 Arena, if you remember that.
Like, in Q3A once you've absolutely nailed rocket jumps, nade jumps, plasma wall rides, and no zoom headshots across maps with the railgun, there wasn't a whole lot left to figure out for most players. There were pro's popping up, though for most people in most servers the wall was hit that a lot of players noticed as well at the time (if they didn't have 8 hours per day dedicated to it like Fatal1ty and the likes). There was a huge benefit to that though, through optimism the mods were very popularly used in quite a lot of servers. I used to really enjoy the ExcessivePlus mod, and a lot of players were on it (most people used it for trick jumps, and the constant health regen made it harder to kill others so it was a playground to practise your skill but rather fun too).

It's a shame the CoD team isn't into the modding scene. Maybe too much money to be had with yearly releases instead...