Not using Cloudflare means I can't access a site that I don't run that has chosen to use Cloudflare. I can choose not to use that site, but my life will be lessened for that, so not using Cloudflare blocks me in that way.
> What on Earth makes you think that they are any sort of gatekeeper of the web?
Unfortunately, site operators have to operate on the Internet we actually have, full of DDoS attacks and wanton scrapers, so a sufficient number of site operators have chosen to use Cloudflare, so as to reduce their burden, so in isolation, yeah, sure, the problem is that in aggregate, they do have keys to the gate of sufficiently large swaths of the Internet, that they are de facto gatekeepers of that particular portion of the Internet.
If you are privileged enough to be able to opt out of that portion of the Internet, count yourself lucky!