Yeah, it kind of was a Leo only club. They don't have a desire to learn it because that's the way it was written. It could have been written any number of ways. Why not show it like you stated above with Raph's lack of patience, Mikey's lack of focus and Donnie not believing it. Yes, Leo picking it up would've still came off as him being the best but would've lessened the blow if all the others were included and at least tried to do it. It just seemed a lot like favoritism to me.
Leo saved the day in Clash of the Mutanimals and in Deadly Venom and got praised both times. It was too soon with only one episode in between so it came off as a Leo love fest. If it were spread out, maybe it would've been more tolerable. I found it very unsatisfying that at the end of the Clash of the Mutanimals they all talked about the mutanimals being under mind control and nothing of Raph being under mind control, their own brother, like it didn't even matter. What was up with that?
I've heard "have patience" before when I was flipping out about the Dark Raph episode before it even aired and look how that turned out. I'd like to think these last 8 episodes have a lot more in store for Raph but yeah, I'd bet the bank that it's not going to happen.
Judging from what I've seen so far, I'd say it's the later.
See, I could probably forgive what happened in season 3 if they make it up by giving season 4 to Raph and season 5 to Mikey. If there is no season 5 then give season 4 to both Raph and Mikey. Like you said, Season 2 seemed more Donnie centric and season 3 was more Leo centric. Either way, I'd like to see more happening with Raph and Mikey.
As far as the whole crack in the shell thing goes, maybe we'll get it. Maybe we won't. Look what happened to Mutagen Man being a major part of season 2. I'm not too hopeful.
Yeah, he has changed. There's a lot less of him and a lot less character development so I can't see how you can come to the conclusion that he is getting more character/ central focus. Yes, he was handled very well in the first episode of season 3 with him watching over, comforting and lifting leo's spirits but that was only one episode and then he was captured, turned into a dog plant and then a flower.

Him being shoved to the side, being the damsel in distress became the norm after that but hey, if that's what you believe, no harm, no foul.
