I agree with the last part. Not so much the first part. I also think the deleted scene of him and Zuri didnt help in regards to T'Challa's feelings.
Again he was near 40 next to the King most of his life. So when you're directly influenced by a standard so long its not as easy to break free. He hears Nakia's perspective, but no new king is making major sweeping changes a week into the job. Unless there is something that turns it on its head.
Also gotta factor his father just got killed outside of Wakanda the moment he tried to open up. So some of the lack of positivity is due to grief and a bit of resentment.
The subtext is very thorough in the movie. My only issue is giving T'Challa's feats to Shuri.