And all of that was caused directly by the UN? Or was more complicated than that, and the UN could do much as the veto powers blocked or delayed things? I'd say it is rather the latter.

There were UN troops in Srebrenica, and their failure is a well covered topic. There are multiple resolutions against Israel, the first from the Suez crisis. Most just get ignored, not the least due to US vetos. The Iraq invasion was a purely US thing that had nothing to do with the UN, some NATO members supported it but not all.

There is a difference between causing disaster, which the UN didn't, and failing to prevent it, which the UN does. Expecting perfect results from one side and no results at all, or close to jone, from the other is just disengnious.