Vegeta showed a lot of growth near the end when he stopped caring about being better than Goku. Master Roshi overcame being a pervert (which I know, who cares lol). Beerus showed more compassion though really... he probably shouldn't have.Like what really was Super? Goku getting a hard-on for strong fighters. No real plot, no character development for anyone except maybe Gohan, Krillin and Android 17 but really, who cares?
GT to me was a show that had a great concept, but failed execution.
They could have dragged it for at least 100+ episodes.
I was thinking it was going to be a good 100 episodes myself but only 64? It felt like once it really got going, it just ended.
A lot of people disliked Goku turning into a kid. I honestly didn't really care, I don't think the show would change my perspective on it whether he was a kid or not. If anything, they could have done something like having another character turned into a kid like Chi Chi, Bulma or Master Roshi. I don't know, just throwing names.
I liked it because it added a bit to the story. Like you felt like Goku could really go on forever. I didn't like how it ended though with him just jumping on the dragon without reason. Why would the dragon take him anywhere? He didn't owe him anything. He never undid all the damage either. He just brought people back so they were left to clean up his mess. I'd be pissed.
Second mistake was having Pan be on the flight. Really should have been Goten and they could have pushed Goten and Trunks as the top new Z fighters. Vegeta also being a part of it would have been cool too.
Pan could have snuck on the ship with them. I guess it made the quest for the black star balls harder given that Goten and Trunks wouldn't have screwed up as much as Pan and Trunks did.
Third mistake was rushing everything. Super Android 17 arc could have been at least 15+ episodes but for some reason it was only 6-7?
This kind of made me mad. That should have been much longer and the fights with the dragons should have been longer. Like at least 2 to 4 episodes each and capping off with a good 12+ for the last one. I feel like the last 20 or so episodes were very rushed and while I enjoyed them, it kept me from really enjoying them like I did with the Cell Games or the Planet Namek run.
As for what you could do now that you have finished GT? They have a movie about Goku Jr.
It's not that good, it's super laid back. Almost on a Dragon Ball level laid back. Don't expect anything insane from it if you choose to watch it.
I already watched it. lol I didn't mind it. I already noticed some similarities in Dragon Ball and the movie and I only watched 2 episodes of that. Like Pan running on the log for example. I think it was more a less a fan service movies. Like look, Goku is still here but we have a new fighter in Goku Jr.
What they should have done with GT is continued it in a way to build up Trunks and Goten like you said. Gohan would have been prefered but he was already too family oriented to change back. Goku could have pissed off like he did but then Goten takes head seat with Trunks by his side and we get to see what it would have been like for Goku and Vegeta to have been on the same side from the beginning (in a sense).