Power can only achieve lift through thrust.
Power doesn't achieve lift. Wings do that. Perhaps you meant to say that thrust imparts motion causing airspeed, causing lift, but thrust doesn't create lift.
"an airplane with a windmilling propeller glides farther and differently than an airplane with a stopped propeller"
Good catch. That should have been written the other way around. An airplane with a stopped propeller glides farther.
With respect to the glide ratio of the airplane and it's L/D ratio, while in perfect theory the two may be considered mathematically identical, they're not. An airplane in a power off condition which provides a given glide ratio does not provide an equivilent indication of the drag to be overcome in a powered situation, considering the windmiling propeller. A windmilling prop will generate drag in excess of a plywood disc out there, of the same diameter as the prop...that's a lot of drag. To attempt to make a comparison between a gliding airplane with a wind milling prop, and the power required to sustain flight is not the same, and not comparable (is not identical) to the drag incurred in a power-off, windmilling glide.
As an example of a worse-case scenario in a light single, I flew a polish M18 Dromader for about seven years, with several different types of powerplants. These were turbine, but piston vs. turbine is really irrelevant here. With a TPE-331-10 powered airplane, retarding the power to idle produced a glide ratio of approximately 1-2:1; from level flight the airplane could slow down so quickly it would throw me forward in the harness and required application of full forward stick to keep from stalling. It was a useful characteristic for the type of flying we were doing, which involved high angle descents into terain, etc. (not a desireable characeristic in a typical light pleasure airplane).
Despite such a dismal glide ratio, the airplane had excellent performance with the power pushed up. The drag which caused the poor glide ratio was due to the propeller at idle, in a windmilling state. (it wasn't particularly impressive in a failed windmilling state either as I can attest from experience). To equate the glide ratio with the power required to fly the airplane would be a highly incongruous. The L/D ratio in a glide isn't comparable to the L/D ratio under power...and one cannot simply say that an airplane with a small powerplant and a poor glide ratio can't be made to fly on that small power...because the power required to fly isn't the same as the power to overcome the drag in the glide. There's less drag in a powered condition. Glide ratio doesn't necessarily equate to a powered state.
Another airplane which I used to fly, which is no longer in service, was a large four engine airplane with radial piston power. One engine at idle, not feathered, could prevent sustained level flight on the remaining three. While most here aren't going to be flying that kind of an airplane, it's an example of a situation in which only one quarter of the available propellers are producing windmilling drag and yet the airplane is still in a highly impaired state...with three more identical engines still functioning perfectly, attempting to sustain flight. The windmilling prop can produce substantial drag which isn't present during a powered state when the engine is driving the prop...to suggest that the power required to sustain flight is comparable to the drag produced in a windmilling glide is incorrect, and that applies to a light single as much as a large four engine recip.