Larsen might not quite be Dallas Thomas bad, but he's very, very bad. I think the difference might be that at least Larsen isn't penalized constantly.
People will say these are 'excuses' for whoever the quarterback is, but it's the truth. The guy has been a matador. As the NFL evolves, coaches and personnel guys have realized that interior pressure is a critical part of the game now. The guard position -- all ridicule from people like Dan LeBatard aside -- is actually pretty important.
Sadly, I put this on Gase. Gase had experience with Larsen and must have certainly signed off on bringing him to Miami as a primary backup interior OL / potential starter. He wasn't good last season, but he did have a serious injury that he had to play through. This season he's been even worse with no injury excuse that I know of. The guy is just a bad football player.
Under Philbin and now Gase, it's been almost an outright refusal to play physical football.