with flaps lowered your Clmax of the aerofoil increases but your stalling angle decreases.
Really!
Sure CL increases but I think if you do a bit more research you will find that tha stalling angle remains pretty much the same. As Mr Vortex mentions the chord line has changed
The deck angle decreases but the stalling angle isn't changed.
If the effective angle of attack of the wing decreases don't we get more range of angle of attack , as the particular aerofoil will always stall on the critical angle of attack?
The Cd increases to a much greater extent than CL so so far as the wings efficiency is concerned flaps don't help. You need more power to overcome the increased drag.
Flaps have two purposes:
1. Increase the lift thereby reducing stalling speed to give slower takeoff and landing speeds allowing shorter runways to be used
2. Increase drag to help slow the aircraft down