I'm not sure about the gpu, but the i7 and 16gb a memory should be able to run the game. Try using activity monitor to see where all the processing power is. If your computer is just overall extremely slow however, you could try factory reseting the device.
Viewing post in Stick It To The Stickman comments
I play this game with nothing else, that I know of open, I quit everything. I have used an activity monitor at times and the CPU usage tends to kind of spike and just go crazy.
At the beginning of the level it is usually using around 60-70%
but when doors open to let in more people my frames tank and reach 0 at times and I can have these moments where my whole computer freezes
Once everyone is dead there is much less cpu used 30-50%
I am currently going through my activity monitor to try and eliminate cpu cycle hungry tasks