I agree that the world should pay far more attention but this is an unfair characterization of the UN.

First of all, the UN are putting out regular updates and Sudan’s UN coordinator thinks they have got the main players to agree to dialogue:

The resident U.N. humanitarian coordinator for Sudan, said on Friday that the beligerants committed to establishing a Humanitarian Forum, with U.N. participation.

Secondly UNHCR are also trying to deal with a cholera outbreak in Sudan at the moment and literally just sent the 6th flight of humanitarian aid:

The plane delivered more than 33 metric tonnes of supplies for cholera response, including medicines, laboratory supplies and equipment, as well as reproductive health kits for the UN Population Fund (UNFPA).