bjj is different from wrasslin, it allows choke holds and joint locks. Doesn't matter hoe big you are if your leg is bent the wrong way or your arteries are forced closed. There was a park ranger once who killed a bear by shoving his arm down its throat to lock its jaw, then he blood choked it by biting its fuarkin neck. He then bashed its brains in with a stick after it was KO.
You're right that rolling around on concrete isn't fun, that's why I want to learn judo, you still get submissions but it's focused on standing up while making the other guy roll around on the concrete