If you think that the lift produced by the wing as its angle of attack is increased at rotation, is not the main reason that an airplane gets airborne then take a look at planes taking off and watch the wing flexing. Its a cleat indication of how hard the wing is working at lift off.
There's no way that the jet thrust being forced downward is the main reason for the airplanes initial lift off. It plays a part, but it isn't the main reason. Its the lift from the wing. Even if you remove the engines so long as you can somehow accelerate the aircraft to around rotation speed it will still fly, jet thrust or not, take a look at gliders.