Like if you're holding block and you read a throw attempt
If you're holding block then you didn't read the throw attempt.
I honestly don't have any technical gripes about MK9 that aren't directly related to bugs. I switched to MK9
because of the ridiculous inconsistencies in SF4, which heavily invested players incorrectly describe as design features (teleport bugs, wildly inconsistent and non-conforming hitboxes, terrible balance, ridiculously heavy emphasis on 1 frame links, option selects, input glitches like crouch teching being part of the meta game, having to count frames to do safe jumps, the input buffer getting cleared by the startup of Viper's Seismo Hammers, generally horrible balance, the list is endless).
MvC3 has its share of serious technical issues as well, what with wavedashing being near-useless on some of the characters that need it most (Haggar), Capcom's unwillingless to nerf X-factor level 3, useless assists everywhere, characters with easy access to mixups which require the defender to think but not the attacker (Wolverine), and the new mashing mechanic (which made me decide not to get Ultimate).
Another technical problem across all Capcom games is the fact that they inflate the execution requirements needlessly on many moves, introducing an element of artificial difficulty and forcing you to fight the game more than your opponent. Fly/unfly/float combos, horridly antiquated diagonal charge motions, and everything Viper does could all be implemented with half the button presses. Let's not even get into how much more married they are to their primitive early 90s character designs (move-wise) than the MK-franchise.
The worst MK9 has is that air fireballs are slightly too good, you still can't block out of dash cancelled moves, there's one serious reset combo left, and tag mode needs its meter rewards tweaked. As far as systemic issues, that's genuinely all I can think of.
I say it without hyperbole when I say that MK9 is actually the closest I've ever played to a basically perfect competitive fighting game. It's the most polished game I've played since Garou: Mark of the Wolves, and MK9 has more than 3 times as many characters.
I think we have it pretty good.