Let me start off with this; I fully intend on buying the game and giving it my all to learn and become competitive in this game.
However, and I'll admit this because Mortal Kombat is the only fighting game I've ever focused on, I was lost and confused without my block button and dash cancels, lol. My first impressions were this, in this order: "Wow, this is a lot of fun....","Wow, this is very different than MK9's controls...","WOW I'm going to suck at this game....","Wow...I'm starting to get the controls and I'm landing some combos...", "Wow...I'm going to rock with Catwoman!!"
So, for me anyway, I had to just dive deep into the unfamiliar waters known as Injustice, and although at first I was pitying myself, I now know I just have to learn and study this game before judging how I'll do. With that said, I can remember thinking to myself when MK9 was first released, "I'll never be able to land those 45% + combos...EVER!!!"...now I can do 50%+ while drunk and in a coma.
Just gotta give it time...and give YOURSELF time to adapt. It's just the demo...