Hulkamania didn't start until later. That was a significant amount of time because as you mentioned, territories. Still counts in this example since Bryan has only been solo for 6 months.
Rock was mid-card for a loooong time with the Nation of Domination, hanging around with the IC title in a feud with HHH, etc. He only got the push later on when he got involved with Austin and McMahon.
Michaels wasn't the super super star he became until DX came about, which was much later in his career.
Austin could never get that shot because the McMahon storyline kept forcing him to lose. Bryan is getting the exact same storyline right now with HHH causing him to lose over and over again.
Hulkamania didn't start until later than what? His defeating the Iron Sheik in early '84 was the birth of Hulkamania. Hogan spent like two years in the territories before his first stint in the WWF, and he wasn't even a full time wrestler during that time.
Rock was only in the NOD for about a year. That's not a very long time at all, especially when he was still a rookie who was coming off of a disastrous stint as a face. From greenhorn to WWF champion in three years is the definition of a meteoric rise.
As for Michaels, again your sense of time is probably distorted by your youth as he was in DX for less than a year before he retired for a few years. His career year in terms of a push was '96. But during that year he proved to be so unreliable as a top guy that he was demoted, probably very willingly. Of course he had a long path to being The Man, owing to the fact that he is a small guy who broke in at a time when being a very large guy meant everything. It was only after he upstaged Diesel at WrestleMania XI that Vince fell madly in love with him and decided he was the next "it" boy.
Austin was by far the biggest star the WWF has ever had by the time he started feuding with McMahon, and you shouldn't confuse his being scripted to lose or his not having the belt at a certain point in time (although he had numerous title reigns) with his not being pushed. The whole storyline was that he was constantly being screwed by Vince, so whether he won or not there was no doubt in any fan's mind that he was the top guy and that he should have won. In fact, Austin was so big that putting the belt on him was completely redundant. The belt is in many regards just a prop to say, "Hey, look at this guy! He's the best!" Austin didn't need that.