>Why aren't we actually prosecuting violent crimes?

We are, but not very successfully.

This thread below (now locked by the mods) covered how that guy, even if arrested for a felony, has a system stacked in his favor (15 to 1 to not get a felony conviction).

https://www.reddit.com/r/nyc/comments/11j3msr/comment/jb1i9df/?context=3

By reddit standards, that thread had a rather cordial and informative discussion about the topic.