As a potential lack of personal investment in character.

If you and many others are correct, and leveling is a time sink which is negative for the average (very busy) player, then it first warrants some study to attempt to quantify this effect in some way.

If you guys happen to be incorrect, and making skill learning rapid could be adjusting the game to the point of people being entirely uncommitted to characters. This could be extremely detrimental to the MUD. Rather than having any investment you would see characters rolled and deleted in a short space of time.

Where does the optimum point between a trade-off personal time and skill learning rates lie? Hard to quantify, but I think it warrants some attempt at quantification, or at least further exploration before tinkering with that specific in-game mechanic is even considered.

A lot of people seem to not have time to play generally, and believe that altering skill learning rates, or leveling speed, will be CF's silver bullet. I am not sure if that would be the case, and I don't know how anyone could retain their objectivity and maintain a position absolute certainty in that type of change being entirely positive.

So yeah, again, not disagreeing with you but it needs some kind of further study to reduce the risk of potential unintended consequences and to better understand the core factors for the overall community.