I will remember Injustice for it rekindling my love for my two favorite DC comics characters (Hawkgirl and Martian Manhunter) introduction of legit grapplers to NRS games and awesome character variety.
There is not a single game in existence where everyone likes every mechanic or trait of a game and Injustice is no exception to this. I enjoyed the game, my only gripes with the game were interactables being so damaging while simultaneously being unblockable and I feel like walk speed could have been better as that would make it more conducive to a better footsie/spacing game. This is not to say that footsies and spacing cannot be played, it's just a bit less fluid and enjoyable.
Pushblock, down 1's comboing into specials and the dash/backdash meta were all interesting to me.
I have my grievances about MK9, but the one thing I loved about MK9 was the walk speeds, baiting out a move like Kitana's forward 2,1 and full combo punishing is a super satisfying feeling.
I also felt like I could play people across various tier positions in Injustice and felt like I could be successful at majors, while I never felt that way with MK9 playing people in the low tier or lower mid tier and as the game went on even the mid tier.
I didn't play a 50/50 mix up character as a main and when I fought players using 50/50 mix up characters, there was never a time where beyond salt I could objectively say a player is inferior and is merely winning because their character has looping 50/50 mix ups. We don't need to like all these tools, but in my view, to discredit a player over it is just absurd.
It seems like Mortal Kombat 9 and Injustice when grouped together as a whole have been stepping stones and seeing NRS learn from their mistakes over each game is really exciting and I cannot wait to play MKX.
TL;DR Every game has issues and high points.