The controls are too slippery .
Since you are using unity ,I'd recommend you either lower the sideways force or increase the friction on the physics material of the cube
I also noticed that this is basically the exact same Game as in the Brackeys How to make a game series,i don't mind you using these tutorials to make your game ,but I think it would be better if you have longer levels and you put at least some new interesting mechanic or system into the game .
That is all I have to say,I hope you fix these issues in the updated version of the game ,can't wait to see the updated version😊
Anyway,have a great day