I don't think that is alone the devteam's fault when a game is released in an unfinished state (I don't know the details as I don't own a copy of SH4).
If the publisher sets a deadline when the game has to be released the devs have to plan very carefully about what goals they can achieve until that point. Modeling a whole new scenario with everything that comes with it, refreshen the grafics engine (is it the same as in SH3 ?) and stuff like that takes very much time too.
Another theory would be that they saw all the good stuff that came from the community and thought that the guys around here are better capable of implementing those nice little (and big) thing which improved SH3 so much and left it to them to do it for SH4 again
