That's really not fair. EVERYONE knew that Lance had uber physical gifts, but he also was coming into the league with the LEAST experience of any of the big 5 QB's. IIRC he only played about 3 games his last season at a 1AA school. I would have been massively surprised he he HADN'T sucked at this point of his career. But his story won't be written this season. Who knows he might never get "it" and the league will always be too fast for him.
Now if you are looking for a bust among the first round QB's. I give you Justin Fields. When you compare his experience vs TB with Mac's, its like night an day. He REALLY looked helpless out there.