I am fully aware that by any reasonable assessment it is completely ridiculous for the most part, but man do I love it. Like >>283367025 said, it is very anime and I think that is a large part of what makes it good.
One thing Symphogear does well is that there is a very good balance of cool and cute, which is in my opinion is a very important part in making a good anime.
As long as one does not take it too seriously, it is very enjoyable.