Unfortunately, I don't think that that is feasible for them. Everyone is a potential rights holder, and granting everyone access to that would likely lead to widespread abuse. Individuals would often claim that they own content that they do not (in order to take down or monetize videos). Even with the limited set of groups that can use Content ID, there is still invalid usage - I remember a few years ago seeing a public domain video taken down because a news company had played the public domain video during its broadcast and then had later claimed that it owned that content. Imagine if everyone had the ability to claim that they owned everything and tried to takedown or monetize a lot of things that they don't own.
Instead, I think it's probably better that they limit Content ID to a set of groups that they trust, where they can actually deal with any abuse on a smaller scale.