The UN is certainly something more than that, and not literally
just a forum.
They have an active duty peacekeeping force of approximately 81K people. While that's similar in size to the active duty forces from a nation like a Peru or Chile, the Blue Helmets have had a de facto quasi-blanket immunity when committing war crimes, and have some pretty horrifying history in places like Central Africa. For example:
"Consider a small sample of heinous cases: in April 2016 Foreign Policy reported that, in the Central African Republic, a French commander tied up four girls and forced them to have sex with a dog. Soldiers from France, Gabon, and Burundi sexually abused at least 108 women and children in a single province. In July 2015, The Washington Post reported that peacekeepers in Haiti engaged in ‘transactional sex’ with over 229 women and girls in exchange for food, medicine, or other necessities.
"Most recently, it was published in the The Washington Post in February 2016 that ‘four peacekeepers had allegedly paid girls as young as 13 as little as 50 cents in exchange for sex in a different camp for the internally displaced’ and ‘as many as 14 troops from France, Chad and Equatorial Guinea allegedly raped and sodomised six boys ages nine to 15’."
https://www.ibanet.org/article/CEBC5F69-A238-49BB-B85A-5E8D8...
I'm guessing if one lived in any of the areas mentioned above, the UN would feel about as much like an invading force as just about anything.
The UN as a peacekeeping force was a great concept, but it's had a very mixed history when put into practice.
But it exists, so many people expect it to be a solution to their problems.