By saying "the universe is fields", I'm saying "it's distributions of energy across spacetime". That's seemingly a consensus. Why demand that that energy must also form into strings or even tinier spheres or spheres in an alternate dimension or something? We have described fields in detail, I say Mission Accomplished
I imagine you could use that argument to shoot down pretty much any explanation.
I think principal bundles come closest to what physicists call fields. Though I'm holding open the option that really the things in most equations are more like elements of the corresponding Lie-algebra.
This should tell us that fields are useful in their own right, without referencing particles.
