It is not an improvement of the series just because of those two things:
It is floaty and stops combos, tech skill is VERY limited, the thinks you already listed like MK, chain grabbing completely shutting down some chars, the "camp or lose" mentality.
Melee can combo, chaingrabbing (other than dysynching icy's) is limited, tech skill is much higher, you do not have to camp to win, there is no single one char who is better than all other.
So yeah, there are your reasons.
But, i will re-emphasize that brawl is a GREAT casual game, and is still fun competitively.