Slice of life works if you have relatable characters and problems, while message of Onion Gang was good, the overall episode isn't that fun to watch because of narrative purposes. Steven is the only character with dialogue in a group of six people, that and Onion and his friends as characters aren't very relatable.

"…goes nowhere."

It's called slice-of-life, people. Not every episode needs balls to the wall action or deep plot revelations about the past.

These characters supposedly have lives outside of the action bits and that's what these episodes show us.

Now, if you think slice-of-life is a bad genre, that's a completely different topic altogether, but that too is still just a subjective opinion.