WKRs are free-for-all world bosses. Technically it's group content, but there's no coordination or teamwork except by happenstance. There are many people in the same place with the same purpose, but all acting individually. That's not the same sort of content Delve is. Delve involves planning and communication. Comparing WKR to Delve is like comparing rush hour pedestrians to a marching band in a parade.