Finished reading Goku black arc in super manga, I am kind of mad how lucky Goku Black/Zamas frequently got

Which is why I don't feel angry at all about Goku using the literal deus ex machina button to solve the problem. Zamas was frequently getting his butt handed to him and was surviving by pure luck:

1. First encounter between Goku and Vegeta v Goku Black, Vegeta fights him alone, and is about to deliver the finishing blow when Future Zamas conveniently shows up to get Goku Black out of the way. A couple of seconds longer and Goku Black would have been dead, and future Zamas, even if immortal, would not have been able to do anything since he was physically weak. Future Zamas was exploring parallel worlds, so there was a possibility he didn't make it in time.

2. When Goku and Vegeta return for round 2, both of them dominate their respective opponents, but again luck and dumbassery save the villain. Let's start with Goku. He actually manages to pull the Mafuba, perfect solution to deal with an immortal Zamas, but unfortunately did not take the sealing talisman. Talk about dumb luck.

3. On Vegeta's side, Vegeta once again completely dominates Goku Black, and is obviously winning. But Future Zamasu decides to try fusion to prevent their defeat. Vegeta takes too long to launch the final strike and fails to prevent the fusion. Had he not spent so much talking and had just gone for the kill, there would be no Goku Black to fuse with.

4. Vegerot vs God Zamas, Vegerot is beating up Zamas badly, and the two of them are about to launch their final attacks at each other. Kaioshin comments that Vegerot seems to be as strong as the gods, and God Zamas is obviously worried. But, just before Vegerot launches what he so confidently believed was the final attack to eliminate God Zamas, the fusion breaks away. So convenient for God Zamas.

5. Goku final fight with God Zamas, Goku suddenly pulls the Destruction move on God Zamas, which seems like it will eliminate him. God Zamas decides to cheat and use Mai as a body shield, forcing Goku to stop. God Zamas would not have done this if he was sure he would regenerate, so had to resort to dirty tactics.

Tl;DR: Zamasu was just full of luck, over and over again, he was getting his butt kicked a lot in the manga and had FIVE instances which he should have died if it weren't for insane luck or Goku and Vegeta hesitating for a few moments. So yeah, I don't feel any anger at the God Button being used, Zamasu true power was god levels of luck.