They are definitely in a tough spot. Generally, I believe that good GM's don't necessarily need to tank or blow it up to get better. Teams that become contenders off the fruits of their tanking aren't as common as people think, and being "mediocre" isn't quite the death sentence that people make it out to be. I think you can get out of any spot by making a good sequence of moves. If Masai was running this team, for example, I would say they necessarily needed to tank. They just need to let him work. It's easy to forget that they made a WCF which is a level the Jazz haven't reached since DWill/Boozer days. So even if they are on the tail end, they had a decent run.
I'd agree that they should have traded CJ. For me it's less about the fit and more that CJ has just been overrated as a player. He's really good, but he is exactly the type of player that gets overrated by consensus. Most of his value is scoring, he's not hyper efficient, isn't a huge playmaker, doesn't defend, fun to watch, loved by his peers ect. At some point they probably should have sold high on him. Even if they didn't trade him, I think they just didn't get enough from their wings. Aminu and Harkless were ok, but really capped their team's ceiling. That and their bench being a revolving door of underwhelming bench players.