In a model without copyright, it wouldn't matter whether a work was derivative, or whether it depended on the "original creative assets"; what would matter is whether people found it useful, interesting, and worth supporting/promoting.
(As for the comment on decentralization of services, I'd agree, but at the same time that particular set of problems also wouldn't exist in the absence of copyright.)
However, if the underlying question we're asking here is still whether copyright adversely affects other potential economic models for creating and distributing new works, I think my original point remains valid. How would the scenarios you mentioned support alternative model(s) that would be more attractive to creators than what we have (or at least, should have) under some sort of copyright scheme?
As I argued in another post, I don't think copyright should ever become an artificial tool to limit communication or interoperability, and as such work necessary to that purpose should indeed not be subject to copyright. It already isn't, to varying degrees, in various jurisdictions.
False takedown claims and the problems that result are more a symptom of allowing centralised hosting of content than anything else. YouTube and the like have no obligation to continue hosting anyone's content if it causes them trouble, regardless of the legitimacy or otherwise of any complaints. As long as there are also no real penalties in law for malicious or negligent actions by big rightsholders, you're going to get this sort of problem anyway.
There are already supposed to be provisions, under banners like fair use or fair dealing, for various applications of works that don't prejudice the original intent of the copyright. Here again it's clear that regulatory capture is hard at work undermining the system, but likewise here again that's due to weak political leadership rather than an inherent problem with copyright.
The areas you mentioned where I'm not so sure are things like remixes, fan works, and mods. In many cases these derivative works do depend on the original creative assets for most of their value, and as such perhaps they should not be exempt from the normal copyright provisions.
In short, I don't see any of those as particularly compelling examples against the basic idea of copyright as a temporary monopoly on reproduction of creative works, subject to reasonable limitations of scope. Rather, I think they are compelling examples of how badly copyright laws have been captured and distorted over time by powerful special interests, particularly in the US, and to some extent of the dangers of giving up control of our own content to third party hosting or distribution services with their own priorities that don't necessarily match our own.