I've done that before.
There are some legitimately great theme songs out there. Epic, memorable melodies that you never fast-forward past, even when you're binging on ten episodes in a row. "Oh man," you think, "I could listen to this theme song all day! Da na, da na na na, da na na na, da na na na..."
But the theme song isn't just a piece of music that stands on its own. It's part of a ritual. It happens every time you watch your favorite show. The theme song means that the show is starting.
This is why taking a theme song out of context can be dangerous. It dilutes the anticipatory power. The Community theme isn't just a great bit of music, it's a great bit of music that is always followed by an episode of Community.
That's why I take theme songs in moderation. The Game of Thrones theme is epic, but would it have the same punch if it were the theme song to every show? Would it have the same impact for My Little Pony? Well, maybe, but that's beside the point. Divorcing a theme song from its source is a dangerous business; you might as well just take any ol' song and use it as the theme song and hang on holy shit that's not seriously a thing is it? Oh geez I was joking.