Well, in due time, we'll have effective combos... Remember the transition from ssb64 to melee?
In smash64, hitstun was so great, 0% to death combos were common and the tier list was almost made around who could perform such combos and who couldn't.
In melee, hitstun was reduced. But in due time, short hopping and wavedashing opened pathways for new combos. Advanced techniques brought in a plethora of new options and improved gameplay to the max.
In brawl, hitstun was reduced even further, so much that combos seem impossible. The only moves that truly combo are rapid jabs into a wall, moves that combo into themselves (shiek's ftilt, and many multi-hit attacks), and select character's chain grabs. All other attacks can combo, just not 100% fool proof. In time, one lucky person will "exploit" the game in a way that will magically improve gameplay, similar to what happened with the discovery of wavedashing in melee.