This is despite the fact I use ControlD as my DNS of choice, and I'm already going through a VPN connection so Cloudflare doesn't see squat.
Proton, however, really should be using ControlD or Quad9, though.
Proton uses Cloudflare
The VPN traffic, which sees your real home IP (and packet size and timing), flows through Cloudflare to Proton.
This is an undeniable conflict of interest, because the websites you're hiding from are also on Cloudflare.
In this epic meme slide show "article" with humor, we quickly present the critical facts you need to know,
https://simplifiedprivacy.com/proton-vpn-and-mail-use-cloudflare/outright-negligent-harm.html
If you care about freedom tech, please share my words. Because "giving a shit" is the only way things will ever change.
Discussion
I believe you have a fundamental misunderstanding of Cloudflare based on repeat comments I've seen. They are far beyond just DNS, but the websites themselves are pointed to them. Please review our educational materials, as it's not voluntary.
How A-record pointing works:
https://simplifiedprivacy.com/cloudflare/index.html
Fingerprinting:
https://simplifiedprivacy.com/browser-fingerprints/updated-every-5-minutes.html
In general on why CF is bad,
https://simplifiedprivacy.com/why-and-what-is-arweb/arweave-website-creator.html