Quite a few whiffed neutrals are extremely hard to punish due to active frames and input latency. So improvement on neutral would be good to see.
I also feel this game is extremely combo centric. So bring back proximity normals which can be cancelled into specials whilst normals from outer distances to be used mainly for pokes.
Also related to the combo centric playstyle problem is crush counters. I personally feel that crush counters is a major problem that really limits playstyles. For example you've got the opponent in a block string with plus frame advantage, if you want to throw another normal your best option will almost always be the normal that crush counters.
You have your opponent in a downed state and you want to do the standard throw or meaty, the meaty option ideally is always the crush counter version incase they press a button or jump.
Being able to V-trigger cancel most normals also leads to the combo centric bullcrap that is SF5 once again. Once players have it, they will spam their best normal over and over to hit confirm into V-trigger then combo.
(This next part is not a KI vs SF5 flame war bait, I just want to state why I feel combos work well in KI but not so much in SF5)
Killer Instinct the combo centric playstyle fits it well, because it still allows you to break combos, you can also predict a combo breaker and counter that with a shadow counter. You also need to decide whether it's worth the risk of going for a full damage combo or shortening it to reduce the risk of getting countered and getting less damage out of it.
To me what made Street Fighter the Street Fighter I know was that the moves/supers were specifically situational requiring heavy decision making. Using supers in juggles meant you would not get the maximised effect of the super, now with critical arts it goes into full cinematics pretty much as long as the first hit lands.
So in short I feel SF5 needs to stop forcing ideal options for each situation, give us options with varying upsides/downsides and allow us to be more creative. I got close to Plat (super gold nearly ultra) players still do the same shit over and over, I watch streams same shit, same play styles.