I mean really cold cache from the above user is at 5000ms that's pretty horrible. When I tried I got 2800ms. Take a look around it seems to be mostly from fetching static content which is a classic problem CDNs solve.
One doesn't even need pro. In our use, Cloudflare's pages.dev and workers.dev serves single-digit TB traffic with triple-digit million hits at $30/mo. We pay $0/mo for origin servers since there aren't any.
People have been citing $30/month. Even if you value your time at min wage, its probably still cheaper than setting up your own varnish (and that's assuming you don't care about improving the last little bit of latency with geo located edge servers)
To answer the actual question - its the obvious answer. They make a product that works well and is relatively cheap. Is it without drawbacks? obviously not, nothing is. However, for a significant segment of the market the value proposition makes sense.
