Why does a proxy server need to decrypt traffic to serve it? Why can't it simply _act as a proxy_? What Cloudflare does is dangerous to the integrity of safe b

Why does a proxy server need to decrypt traffic to serve it? Why can't it simply _act as a proxy_? What Cloudflare does is dangerous to the integrity of safe browsing, for a variety of reasons. And their aggressive marketing to convince a lot of tech-ignorant people with low traffic websites that they need a CDN is harmful. Is it too much to ask that their service at least operate in a way that doesn't poison the internet they're getting rich from?