Resolvers should aggressively cache the root zone. And the traffic shouldn't be any worse than what google or cloudflare resolvers are seeing.
What are you basing that on? How many people do you think are really using Google DNS or Cloudfare DNS? I think even if just Comcast changed their defaults, the root servers would see a order of magnitude more traffic than Google or Cloudfare see.
One of the reasons DNS is hierarchical is for load distribution (and performance). Taking this design principle and all of a sudden throwing it out the window would likely have major consequences for a system that was originally designed and scaled with it in mind.