Fair point.
My counter argument would be that those other 4 players (Sterling, Mahrez, KdB, Cancelo) the poster mentioned as being inconsistent are also basically playing the same position most of the time (I don't agree that Cancelo is really inconsistent), while Foden keeps playing between LW, RW and Attacking midfield with Pep unsure where to play.
If I may chime in, I think this is a Foden AND Pep problem, and not really down to Foden alone.
Yes, Foden has to improve, he sometimes is TOO eager and has to learn to just control the midfield like Silva, which will take time. But... unlike Silva and more like KdB he is more of a numbers guy, goals and assists, which is almost the opposite of whats needed.
One might argue that why can't KdB in all his maturity become the "controller" with Gundogan as he should be more discplined than Foden, but Pep wants KdB to create and be risky because he is elite here.
If Foden can learn to combine the best strengths of Silva and KdB (he is closer to KdB than Silva) over the next years, he is basically the best player in the world imo (after Messi retires).