If it is irresponsible to utilize the services provided by companies under the jurisdiction of the United States, then using much of the internet and Firefox itself is irresponsible.

The user made a conscious choice to trust one specific American company. They do not want other companies they did not personally "vet"-- with whatever weird and personal criteria they feel like -- added without their approval. This shouldn't be this hard to understand.

And they have the option to not utilize this feature or change the settings to a service provider they do trust.

The threat vector is understandable. Not making the choice to mitigate it is what does not make sense to me. Cloudflare is not an unknown operator. You can study their past behavior, their beliefs, and how their services work, and make that choice.

Saying 99% of people accept the defaults and claiming this is bad without learning about what the defaults are or how to change them when it takes a few straightforward steps to do so is what does not make sense to me.

Even installing Firefox in the first place is to make a conscious choice to change the defaults of nearly all operating systems that the vast majority of people on Earth use. It’s defaults will also now have a feature to encrypt your DNS queries to a third party vetted by Firefox. If you cannot trust them then why use their browser?

I’ve studied it.

“Matthew Prince, Cloudflare’s chief executive. “It’s dangerous for infrastructure companies to be making what are editorial decisions,” he said.”

Not dangerous enough apparently.

So? That's not an argument for doing it again. 'Everyone else is taking a bung from the NSA to forward them data', for example, isn't a moral justification to do it yourself (made up example).