Not by network hardware, which is the context of this discussion.
It's also not the type of activity being discussed, which is unauthorized caching: a content provider who uses a CDN is doing so intentionally and while shared local proxies are increasingly uncommon they also respect the Cache-Control headers set by the source — see e.g. https://redbot.org/?uri=https%3A%2F%2Fwww.wsj.com — so again there's the distinguishing factor of authorization.
It's also not the type of activity being discussed, which is unauthorized caching: a content provider who uses a CDN is doing so intentionally and while shared local proxies are increasingly uncommon they also respect the Cache-Control headers set by the source — see e.g. https://redbot.org/?uri=https%3A%2F%2Fwww.wsj.com — so again there's the distinguishing factor of authorization.