As much as i don't even ship Wusako because,..reasons rooted from the old writers who don't know how to write women... it wouldn't really be fair for blaming Wu for still harboring feelings for Misako. Some people could have a hard time moving on regardless if this person is married or not, and Wu appears to fall into that category. Also Garmadon stole his love letter, regardless if that's an influence from Chen or the venom, to hell with that, Garmadon wasn't being completely truthful to Misako regarding that matter.
And Wu was just trying to do what's best for Ninjago, the "terrible decisions" were when he was still pretty young, and he wants to deal with it himself because he doesn't want to burden anyone and it has always been his tendency; many times he's humbled and reminded that he can't do this alone. And those enemies are last known to be either inactive or dead anyways (except the Time Twins, he already counted the date ever since their banishment).
Also when did Morro kill himself? He was dying due to toxic fumes from the FSM's tomb because of his reckless decision to prove he's the green ninja resulted from a naive and unstable emotion regulations as a teenager. He was right to be angry and felt betrayed, yet Wu was only trying to search who the Saviour could be, and is still honored to took him under his wing no matter the circumstances.
Later on, Morro grew up, he understands the situation now, the things he blame Wu for was a judgement clouded with anger (and relatively age and naivety).
And for anything else, we're still yet to receive explanation about the merge on how Wu is allegedly behind all of this.
He can have what he knows, the ninja can have what they know, and sometimes it's hard to try to communicate and talk about it when those problems are what you believe is a consequence of your own actions, sometimes it feels burdening to ask others for help. Wu was basically the heir who was alone to maintain the balance of the whole damn realm (after doing so alongside his brother who is also destined to eventually join the dark force) his father created. It's a heavy burden to carry. But to each their own.
