I like Starlight a lot as a character, and she had some interesting ideas. Her methods were aggressive and manipulative, but effective. If you "liberate" everyone of their special talents, and nopony has more of anything than anypony else, equality becomes not just a convenient political idea, but a reality. The question is whether that reality is worth the price you have to pay for it. I'm sure Starlight thought so; after all, she retained her cutie mark and was the de facto leader. But the other ponies in town had to sacrifice their individual potential for a life that was dull, empty, and scary if they got on Starlight's bad side.
To me Starlight's philosophy had merit, and for a while she made it work. But it wasn't worth the price because it did not bring about true happiness. If there was a way to do that, Starlight didn't care to find it. The Mane Six's interference and her own negative, deceptive leadership ensured that the experiment would fail.