Welcome, SCPX. To your question-

what you've described is done frequently. The thing is, it must gain momentum to achieve airspeed. Airspeed is not created by sitting still and pushing air, you must travel through air to have airspeed.

So while a plane spools up with the brakes on, it's like a boat at 3/4ths throttle tied to a pier. Get free of the line, and it's off like a shot. If the boat is a hydrafoil, it will still need to gain momentum and speed through the water to be raised up on it's foils. Do I make any sense, ever?

::ETA:: While the engine is turning, air flows only through the turbine/prop path/both. In order to achieve lift, you must create airflow over the entire wing. This is why forward motion is required.