What arrogance. Why it is their job to gatekeep this?

It literally is their job. One of Mozilla's roles is to give their opinion on proposed web standards. It's one of the factors that determines what actually becomes a standard. WebUSB is Chrome (and derivatives) only at the moment. You can not like where they landed, perfectly valid, but they were asked.

Yes, but instead of saying "this spec is shit and full of vulnerabilities. Let's work on improving it", they just refused to participate in the discussion. What a childish POV.

I don't think that's a fair summary of Mozillas Position on the WebBluetooth/WebSerial/WebUSB specs. Interacting with arbitary devices has arbitrary consequences, mozilla seems to assume users are not able to understand these consequences and therefore cannot consent to it.

No improvment to the spec can fix users.

Well, the reason is in the links I provided, and the reasoning doesn't scream arrogance to me.

Personally, I think choice is great. Why be upset when you can download chromium (it is supported by pretty much any platform FF is) and use it to do all sorts of stuff with WebUSB, if you are into that?

Still, I would like to see FF disable these features by default and allow opt-in. I don't see a great reason to avoid implementing them behind some "wall" (other than to avoid an increase in a concealed attack surface).

You are completely missing the point just like Mozilla.

This is the same a surgeon saying they refused to perform life-saving surgery on you because they don't believe you understand the consequences of the possibility of dying in surgery.

The average person cannot be an expert on surgery or on browser security it's up to the people that have the education and work experience in there to make those decisions and handle them. Mozilla as another poster said has taken their toys home because they didn't get what they want.