You really don't understand Goku, that much is clear. Intent is what is missing. Goku has saved the earth and the universe, but he has never really tried to do that. His intent is to fight powerful opponents. That's it.
Goku stands for truth and justice? Since when? This is Goku we're talking about. He doesn't care for that. He's the guy that gave Freeza multiple chances to survive and even gave him energy. Frieza the guy that wiped out the nameks, the saiyans and god knows how many other planets. He spared vegetas life because he wanted a rematch. He literally said that it was selfish to want vegeta to live, but simply wanted to fight him again. He let Dr. Gero create the androids because he wanted to test his strength against them.
The reason he helped trunks is because Trunks is his friend and black would be a fun fight. Not to mention he wanted to understand how black had his body.
If you think Goku is written as a superman type of hero then you are wrong. You don't understand goku. He is not a superman type of character.
He may be the savior of earth, but he doesn't try to be. He simply wants to fight stronger opponents and to have fair fights. That is it. He beat the saiyans and frieza, but he has also traveled to another timeline and annoyed Zamasu into fighting him, he tried to fight monaka, he paid Hitt to try and kill him and when he heard there was a god of destruciton, he tried to challenge him as well.
Goku simply wants to have a good fight. He even said so in the last episode when they asked him what he would like to wish for. He said either something for his wife, his kids or a powerful opponent he could fight against.
You seemingly don't understand Superman. Superman is a nigh unstoppable being that struggles every day to do the right thing. He wants to protect the world, he stands for truth and justice. He's basically a god trying to live and help humanity.
Goku is a dude that wants to get stronger to be able to fight stronger opponents. Whether they're good or bad, it doesn't matter to him. He just wants to fight.