is that it helps to keep away hate, racism, trash and dangerous content in most of the subs/communities

No, it reinforces values and creates an echo chamber. In communities that value left wing values, it drowns out right wing values, and vice versa. I learned that the hard way.

A long time ago, I moderated a place that had lot of room for discussion, and people of opposing opinions often had discussions. I then added a scoring system, thinking it would be nice for people to keep track. But all it did was kill the diversity of opinions. People whose opinions were slightly outside of mainstream, saw their opinion getting downvoted and adapted their speech patterns accordingly, or just left altogether. Within a year, what was once a neutral idea thinktank got turned into a giant conservative circlejerk.

Long term result: polarization galore. That site tipped to the right whereas Reddit tipped to left. Either way, you're basically ostracized for suggesting "the other side" may have a point with some things, or to try and encourage to figure out the reasoning why someone might think the way they do.

I sincerely hope Lemmy doesn't follow that direction.