There's absolutely nothing wrong with, for instance, a content provider handing an ISP a box that sits on their network, mirrors/caches content, and serves it up to that ISP's customers. That helps the content provider, the ISP, and the ISP's customers. And I don't think the majority of "net neutrality" advocates want to break that.
When people talk about "net neutrality", the problems they have in mind tend to look like either an ISP extorting content providers to extract extra revenue, or an ISP giving their own first-party services an advantage by deliberately degrading third-party services. For instance, see Comcast and Netflix.
But even then, how do you draw a bright line between "deliberately degrading", "not giving an advantage to", and "not doing anything to address bandwidth problems when they arise"? (Comcast could claim the latter regarding Netflix, even though it seems obvious what it means when they don't arrange additional bandwidth on those saturated links.) What if the ISP provides the CDN infrastructure, rather than the content provider? What if the ISP contracts with a third-party CDN?
How would you suggest writing a regulation that doesn't break CDNs and similar, and that can tell the difference between "deliberately hurting" and "not helping"? How will that regulation adapt when people come up with new ideas to make the web faster?
(One angle I could imagine working: limiting the ability of one company or family of companies to run both an ISP and network services via that ISP. Still hard to write something robust, though.)