Bing has terminated all of its search syndication and API services, and will likely be removed completely in a future version. As it is a struggle to monetise Waterfox Private Search with an ad-supported free version, it’s unlikely it will ever be default and instead will be a subscription-only based service.
The default search engine has been changed to Startpage.
I’d imagine their search results will get slightly better.
I’m not entirely joking because Bing is that terrible.