I agree with most of what you say, Megaman. I also think Skull Barrier should've stayed the same. But I don't agree with the Centaur Flash tidbit.
You could say similar things about Gravity Hold (Gravity Hold doesn't increase gravity in MM5) and Flash Stopper (Flash Stopper stopped time in MM4). Problem is, the screen clearing attacks in the original games were a bit bland, especially Centaur Flash, which didn't stop time, or remove pickups, or give you invisibility frames, or decrease gravity, or do anything other than making the entire screen white, removing some ammo, and damaging enemies.
The pre-v5 Centaur Flash did have the ability to reflect projectiles, but it was hard to use except under specific circumstances, and even then it isn't easy to do, and the projectile reflection ability wasn't easily conveyed, causing me, and probably others, to not know that that feature existed just from playing the game. I personally welcomed the invisibility change, and felt it added some new strategic possibilities.