Imaro
Legend
TBH as a MAJOR 4e stan, I think that the length of combats was one of if not the biggest issues 4e needed to work on. I don't see why skill challenges default including everyone is any more or less an issue then the assumption (that every edition has) that every player is in every combat challenge.
The skill challenge forcing everyone to participate no matter what, at least in my experience, was also often a time sink (along with combat), especially when a player was struggling to figure out a way to contribute but also trying to juxtapose that with something they are good at so they didn't generate a failure.