Rick and Morty season 4 saw Morty keep making the mistake of trying too hard to control his life. The show has done a lot to help Morty grow, starting with him having the authority to not go on adventures with his mad scientist grandfather Rick if he doesn’t want to.
While this is a big change for the positive, Morty needs more than just the authority to say "no". He's no longer just being pulled into big sci-fi adventures, but that growth isn't coming from him. When left to his own devices, Morty keeps making the same mistakes, mostly following in Rick's steps of doing whatever reckless thing that he wants to do. It's clear that Morty hasn't yet learned that he can't micromanage his life perfectly.
Rick & Morty Season 4 Finale: Which Beth Is Real & Which Is The Clone?
Season 4 of Rick and Morty had two episodes out of ten where Morty should have learned that he can't control everything, but he falls short in both. He spends the season premiere, "Edge of Tomorty: Rick Die Rickpeat", abusing the power of death crystals to give him the perfect death. He does the same in "The Vat of Acid Episode", where he gets the ability to play life like a video game and reload from his last save when things go wrong, only to do horrible things in the process.
In “Edge of Tomorty: Rick Die Rickpeat,” Morty constantly saw the way that he would die. His obsession with dying of old age next to Jessica, his high school crush, led to him going on a bloody rampage he was barely talked down from. He learns at the end that he completely misunderstood the context of his death with Jessica by his side (she was there as his nurse), showing him the limits of trying to make that kind of future prediction. He still tries to exert too much control over his life in Rick & Morty season 4, episode 8, “The Vat of Acid Episode”. There, he discovers that, in the process of constantly saving and reloading his life, he’s killed hundreds or possibly thousands of alternate versions of himself to try and get the outcome he wants, which ultimately doesn't even work out.
What Morty does is horrible, but he is at least appalled by it once he realizes. The mistake that he makes, which is the likely source for future character development, is that he keeps trying to make something work that doesn't and causes bad things to happen. Morty is doing what Rick does: whatever it takes to get what you want without caring about the consequences. Morty's possible saving grace is that he does care about the consequences once he knows about them. He's learning bit by bit. He sees that trying to make every part of his life perfect hasn't worked, but he doesn't see the bigger lesson yet. He's getting better, but for right now, still hasn't learned to let go of trying to control things so tightly. Morty is still acting like, if he does it right, he can act selfish and get away with it like Rick does. Season 4 of Rick and Morty has Morty keep making the mistake, and hopefully, he'll start learning from it sooner rather than later.