Can you conceive of a general intelligence that has no capacity for abstraction? And do you not find it possible (even if difficult) to think of general intelligence that doesn't use a WM?

Particularly since our most advanced thinking has far less reliance on our working memory. Advanced expertise brings with it the ability to manipulate highly specialised memories in what would normally be considered long term memory. It doesn't replace WM but it comes close enough for our imaginative purposes!