They did some rebalancing of the grooves, which was fine, but they took out roll cancelling which actually improved the game.
One of the bigger problems (if you want to call it that) with CvS2 is that normals have quite high priority, and specials are not very good on hit/block, particularly fireballs. You don't often see fireball zoning in CvS2, partially because of roll but partially because of bad frame data.
With roll cancelling, a lot (more) of the cast could compete, instead of just getting stomped by cr. fierce with Sagat, and other high priority moves.
SNK grooves have short jump, which you would think would make the game more offensive, but the system is not anywhere close to as offensive as KOF, for many reasons.
Ever think CvS2 was too slow? It's even slower without RC.
Yes there was some super dumb stuff like RC electricity, but people preferred that to having every round take forever.
So it was Capcom's bad attempt to fix their own system, and it took out RC while not offering nearly enough system changes to make it better.
It's like when they "fixed" A2 with A2 Gold. They toned down custom combos and ACs, but they also messed with the priority (read: hitboxes) of a lot of moves and made them worse. Characters felt really weak and people didn't like it.
