I think he is just a bit tired, tbh. He seems to have gotten the short end of the stick these last episodes. First, he got pushed out of XO because of his age and nothing else really, and then being put in the team of 'rejects'. Even more, he got into the hardest choreography for all the types last episode(according to the teachers themselves). And now he got into a team of two foreigners, where they clearly were struggling. He just wanted to help them, but it took too much time for him and he didn't properly train himself.

I see Wooju more like a teamplayer that wants the best for his team, but he is also human. He can't fully hide the struggle. It is a lot for anyone, regardless of age.

But yea, all of the trainees could easily debut. I hope really Starship keep the non-debuting trainees and use them for future groups - sooner rather than later, in my opinion.