1. The burnout/overkill after everything Trunks already went through in the Androids/Cell Saga.
2. Zamasu coming across as more contrived/nonsensical than any other villain in DB history - as well as just plain annoying.
3. The ending, which makes the whole Saga feel pointless.
1. I can relate. He starts the Androids Saga with the feeling that he won't be able to do this on his own and the will to rely on Goku + friends. Throughout the hardships of his arc, he learns to stand for himself and ultimately manages not only to defeat the androids by his own hands, but also to get rid of Boo before he even gets into life. The Zamasu arc completely undoes his journey by making him rely on other people again, going as far as showing him happy that both Goku and Vegeta became so strong that he basically doesn't have to do anything on his own - up to Vegeta's wakeup call by training, he doesn't see any need to improve himself for his future. I also found that quite frustrating, even though quite realistic. As a person who also goes through permanent struggles with her self-esteem, I can say that this fallback into old behaviour is quite realistic - but Dragonball has never been realistic, shonen anime are rarely realistic in general - when a character has had an arc, the growth sticks. There might be flashbacks, but no fallbacks, so I can totally get where you are coming from.
2. Okay, I didn't find him more nonsensical than for example Frieza who just wanted to reign, King Piccolo who just wanted to reign, Cell who wanted to be the best or Buu who ... didn't want anything in particular and just happened to bring destruction. I liked that they actually gave him a reason to think that way, one, that makes a lot of sense from a god's point of view. I found it quite funny that he fused with a mortal to achieve his ways, but felt that was quite fitting - bringing death to the mortals by using one of their own kind. But I can see what you find annoying about him, I kinda liked that about him. He was so weird.
3. Cannot disagree. Yes, it does.
Topic:
The ending of Digimon Cyber Sleuth: Hacker's memory comes to mind. I felt it was an insult overall and ends on a note of "it would've been better if a particular person never had been born" which kinda resulted in another one not being gay (however that works) which disgusted me as a message. Ugh.