Oh I can sort of agree with that for sure.
I mean when he came back to life in the comics he definitely had a renewed sense of optimism and all that, but the Justice League movie fast-forwarded it a bit too much.
His arc in the films was always supposed to be an organic progression of growing into the role over time, but it was indeed rushed through and ruined because people had no patience for character development. I agree with that. He was my favorite part of Justice League but it all felt very corporate-mandated and a bit false.
I could just see/hear Whedon just off camera during the scene with Cyborg yelling "C'mon, LAUGH! Laugh HARDER! WE WON'T HIT A BILLION DOLLARS UNLESS YOU LAUGH!"
