It's a story about how if you have superior vision and understanding to everyone else, if you try to tell them about it they'll get mad at you. Written by a guy everyone was mad at.

Yeah, it does have that flaw: the philosopher who goes outside the cave isn't just in a larger cave, he sees reality, supposedly. And weaker minds reject it because they just can't handle the blinding light of the truth, not because there might be further errors.