What is stopping Shidou from evolving or improving?

As the title says, what is stopping Shidou from evolving or improving? So far, he's barely changed from the U-20 match to the current bm vs pxg match aside from a bit more experience. Other than that, Shidou seems to been stagnant for quite a long time.

It's not like Shidou is on the wrong path or anything, since we clearly see him follow his ego and desires. So infact, I don't necessarily think Shidou is on the wrong path, but rather something seems to be hindering him. Maybe it's a similar problem to Nagi where his overall performance is dependent on who he partners with.

Anyways, let me know your thoughts in the comments down below. Only responsible comments and responses please! Thank you!

TL:DR Something is hindering Shidou and causing him to become stagnant. However, I can't exactly point my finger on what's his problem.