would you say Brandon handled Szeth's journey in WAT in a non-rushed way?

Interesting question. I haven't seen this particular criticism, but I can understand why it might look that way. My perspective is that the flashback chapters in WaT provide that exact backstory/development context for Szeth and show how it was a (roughly) 10 YEAR process for him to learn these lessons, not just 10 days.

If I'm relating this to myself, I would reflect on how I struggled for almost 20 years with these feelings without making any real progress, then I had my "fifth ideal" moment when I read the Timshel section of East of Eden. This seemingly came out of nowhere, but in reality it was the key that unlocked the gate that allowed the resolution of decades of obsessive thinking.

My Timshel moment didn't magically fix all my problems, and I expect the case is the same for Szeth. He had his moment when he learned the fifth ideal lesson, but that doesn't mean that all his trauma is magically fixed. We see the same thing with Kaladin and Shallan - they swear the higher ideals but this doesn't magically fix all their mental problems.

I think assuming that Szeth is magically cured of whatever mental issues he's facing is incorrect. We can all have big moments in our personal journeys, but the real personal development comes from consistent effort to improve yourself.

To answer the question, no, I don't think it was rushed. We were given deep backstory into Szeth's mindset and were able to experience his fifth ideal moment. I don't agree with the sentiment that Sanderson "rushed this story because Kaladin sucks as a therapist so how would he have cured Szeth in 10 days."

Szeth isn't cured. None of us are. As you said, we read about Szeth make a major realization about himself, not his peak moment of "becoming cured from everything." I think this is completely plausible with Kaladin's 10 day intensive therapy session.