Well, without the cutscenes, the Injustice 2 story might last you approximately 12 hours, give or take. This assumes you're playing at a decent pace and not getting stuck on difficult sections for too long.
Sure, the Destiny 2 beta allowed for skipping cutscenes in the story. It's a common feature in many games these days to give players more control over their experience. If you're not into the story part and just want to get to the gameplay, it's there for you to use.
The cutscenes are very important. They help to tell the story. Without them, we would not understand the context of the medical cases or the relationships between the characters as well.