User blog comment:Shigfugjum/Power Creep and the Fate of Older Champions/@comment-26044269-20150902052917

Generally speaking, power creep can be bandaided through simple number tweaks. What I'm most worried about is mobility creep specifically, as these are harder to balance out through simple number tweaks because the utilities mobility provides aren't as linear or one-dimensional as damage's (unlike power, mobility allows for one to do more than just deal X amounts of damage to kill Y).

Besides the whole point of a MOBA type game is to have adequate/perfect imbalance. A controllable level of imbalance calls for a constantly shifting meta game which allows the game to not feel as tedious and repetitive as it would otherwise. Furthermore, complex kits are what naturally come as developers gain more and more experience. Newer champions are mostly aimed towards the veteran players anyway who have mastered most if not all of the existing champions, or at least have some knowledge of how they should be played.