If you say so. Just because you say it is, doesn't make it true. Diana's current power levels have nothing to do with sexism
You're right about them pushing Harley, but they still aren't able to put her on the Justice League as a superhero, and she is still inherently tied to the Batman franchise. If they succeed in turning Harley Quinn into a full on superhero with good sales then I have no doubt that Wonder Woman will become just like any other character and be cancelled once her sales drop, only to be brought back two years later.