A big part of that issue though is simply that the art in the center is way too complicated/detailed. Also there's no contrast between the black horses and the blue field. South Carolina and Alaska follow a similar "symbol on a blue field" formula but I'd rank them solidly above most of the rest as the symbols are relatively simple and easy to identify. Even Indiana's is better because the symbol is so much simpler, there's clear color contrast, etc.

I do quite like the Pennsylvania coat of arms on its own, it works well in printed designs. I just don't think it works well as a flag.