Craig Mokhiber, director of human rights body, accuses the US, UK and much of Europe as ‘wholly complicit in the horrific assault’
The Guardian’s title is a bit misleading I would say.
"[A UN spojesperson] can confirm that he is retiring today. He informed the UN in March 2023 of his upcoming retirement, which takes effect tomorrow. The views in his letter made public today are his personal views.”
So he steps down because he is retiring, not because of the genocide.
You are correct. He has served the UN since 1992 and he did not step down for Yemen or any genocide. It is just his retirement letter.
Also this is mentioned in the article:
He was criticised for posting support of the boycott, divest, sanctions (BDS) movement and accusing Israel of apartheid – an accusation which he repeated in his retirement letter.
and this is the twitter link to the retirement letter