Is it me, or is MKs only consistent elements the uppercut and the Fatalities?
I think there's a lot of things you can point to, especially if you go easy on the 3D games being naturally different.
Obviously there are mainstay special moves and presentation, but you got the layout of HP LP HK LK, Block Button(no crossups), strong jump attacks, projectiles do NOT collide, uppercut, sweep. Then some stuff carried over from the 3D era like strings and overhead/low mixups. More generally, I think MK games tend to have really fast moves that can threaten you from distance like projectiles or teleports