Shit did you all not read the manga? Aizen reached the limits of how powerful a shinigami can be so he got bored. He is now the undisputed ruler of Hueco Mundo because hollow recognize that he is a being that has _no fear_ which is appealing to them. He has the hougyoku and of course by now he has crossed the barrier of shinigami himself. That's the whole point. Even Grimmjow who had an ego larger than the universe cowered before him. Personally I think Ulquiorra and up are VL and they all show him respect. This is not about fanboying Aizen, Kubo himself is telling us over and over this guy is fucking untouchable. You see him even moving when Shinji is centimetres away from his neck? No. He will probably not even move the next chapter either since WW will shut Shinji up.
Check out 3:49, unless Shinji has come up with a way to counter total hypnosis he is done for. He did catch Aizen spying on him before, so maybe he has an idea, but he won't be the one to take on Aizen.