They Wasted A Perfectly Good Plot / Dragon Ball Super

• The Resurrection 'F' arc completely skips over how Goku and Vegeta acquired the Super Saiyan Blue form, with them achieving it offscreen. While this was one thing in the original film, it's quite another in a series that had a lot more runtime to work with. Considering that one of the biggest complaints about Blue was that it came off as just "Super Saiyan, but with blue colors and more power," it would have been an excellent opportunity to define it as its own thing. For that matter, we also never see how Vegeta acquired regular ol' Super Saiyan God, even though it's a form that relies on the power of others and therefore something Vegeta would be reluctant to assume.
• Future Trunks and Future Mai's lives after Future Zen'o destroyed the future timeline to put an end to Zamasu once and for all. Yes, we wouldn't get the Bittersweet Ending of them going to a nearly identical timeline where Zamasu is dealt with before he can set about his Zero Mortals Plan, but many fans would have loved to see Future Trunks and Future Mai remain in the present timeline and become permanent members of the main cast.
  • Likewise, some viewers would have loved to see some interaction between Future Mai and the present versions of the Pilaf Gang, especially when one considers how Pilaf and Shu would have been long gone in the Future Timeline, even before Black came into the picture.
• Many fans pointed out just where the hell was Universe 10's God of Destruction during the Future Trunks Saga. As Whis reveals, a God of Destruction is tied to their respective Supreme Kais (and by extension, the God of Destruction's Angels who are also tied with them). Because the fate of every Future Gowasu except the main timeline one, U10's God of Destruction would have every right to be involved and since Zamasu usurped the right to become a Supreme Kai, they would have at least be involved because their life is tied with Gowasu and later with Zamasu. Funny enough, the god later appeared during the Universal Survival Saga and was revealed to be an elephant, turning him into a literal Elephant in the Living Room. However, when we see him, Rumsshi, talk about Goku, he sounds like an Ungrateful Bastard, not realizing that he would've been dead if Beerus and Goku didn't interfere.
• In the anime, Goku learns the Mafuba/Evil Containtment Wave technique from master Roshi to trap Future Zamasu... only for that plot thread to go nowhere, as Trunks then learns it and traps Zamasu himself. You would think the Universal Survival Arc or the filler arc would fix this, but no, Goku never uses it, meaning the entire sequence was a waste of time.
• Hit being hired to kill Goku by an unknown client. Many felt it had the potential to be a main arc, feeling with Godtube being a thing and the Universal Tournament coming up this could have been a good way to introduce new characters from other universes who heard about Goku's threateningly overwhelming power and want him dead. Instead this ends up being a two-part arc with Goku putting the hit out on himself so he can fight Hit at his best.
• The very episode after Frieza was temporarily returned to life, he quickly backstabbed Goku after making short work of Universe 9's assassins. Calling up Sidra and Roh, he proceeded to outright request to join Universe 9's team. Roh of all people was concerned that he was too much of a Psycho Party Member, while Sidra seemed outright for it for that same reason, given the fact that they're still starved for team members aside from the Trio de Dangers. Frieza could've been enough of a One-Man Army to turn Universe 9 from the loser team to a legitimate threat, while also again leaving a vacancy for Buu to miraculously wake up, Yamcha's Running Gag to have a payoff that wasn't a "Shaggy Dog" Story, or for some other Unexpected Character to fill the spot. But alas, Frieza just calls off the deal without a second thought when Beerus and Whis show up and the Evolving Credits finally replaced him with Buu shortly afterwards, more or less fully cementing his spot as a Universe 7 combatant.
• The idea of Goku putting the whole universe in danger out of his own boredom from lack of opponents by reminding Zen'o of the tournament could've potentially deconstructed his own selfish Saiyan traits and gave him some well-needed Character Development on how he should heed the warnings of others and learn the consequences of meddling with highly destructive gods. It could have also made the gods from the other universes a bit sympathetic as they would have good reason to hate Goku since he put their universes in danger because of his selfish desire for a good fight. But ultimately, with the revelation that Zen'o was going to destroy the low level universes anyway and that Goku actually gave one universe a chance to survive, it ended up making Goku once again an Accidental Hero out of dumb luck, making Beerus and Whis' warning go over his head and negates a chance to give Goku character development knowing he ended up making the situation better instead of worse. It also made the gods from other universes into ungrateful jerks who are unwilling to see that Goku actually managed to give them a fighting chance and ended up blaming Goku for their current situation despite the situation being presented otherwise.
• Goku and Top having their rematch in the Tournament of Power. Considering their fight before the tournament was put to an halt, along with Goku being eager to fight the Pride Trooper leader again (even immediately head towards him when the tournament starts, only for other fighters to get in his way) and Top wanting to pound Goku to the dirt for bringing up the tournament to Zen'o, one would think that they could've finally fought again once they weren't interrupted, more so when Top unleashes his God of Destruction mode. Instead, the rematch never happens as Jiren becomes Goku's main rival and Top gets eliminated by Vegeta.
• During Gohan's sparing match with Goku, he states that he wants to obtain a never before seen "ultimate form" that will be an ascension of the form he's using. The fight against Top could've been the perfect way for him to obtain the new form, what with Top being his toughest opponent in the tournament. Instead, he abandons the fight against him to help Frieza out against Dyspo, sacrificing his participation to ensure Dyspo's elimination and ending up not obtaining a new transformation. However, the promise of a new form was ultimately fulfilled in Dragon Ball Super: Super Hero.
• The idea of the Potara fusion for the Tournament of Power is a neat idea, but only Universe 6 uses it. Universe 2 tries it, but the U2 gods, instead of giving them to Ribrianne and Rozie who are strong enough on their own, give their earrings to Rabanra and Zarbuto, who screw up the process due to one of them refusing to take their helmet off and Kefla blows them up along the Potara. Universe 7 toys with the idea of allowing the Androids to fuse into a hypothetical Android 35 (like in Heroes and Fusions), but the idea is dismissed due to reasoning that doesn't make sense; since fusions are depicted as being stronger than the sum of their parts (depending on compatibility), 35's increased ability to defend themself (or depending on which gender was likely the more dominant personality, himself or herself) should have been well worth the risk of losing two fighters at once, though them not going through with the hypothetical fusion was actually the best course of action in the end, as Kelfa gets ultimately eliminated by Ultra Instinct Goku (revealing that the risk was far too great for them to take on losing two fighters), and Android 18 sacrifices herself to save her brother Android 17 from getting eliminated who proceeds to win the entire Tournament.