It's the reverse. The purpose of the feature is to put known trusted extensions on a whitelist for sensitive sites while blacklisting everything else.

In my case I'd put uBlock on my "yes I trust this extension" list and when I visit my banking website only that extension would be active.

It's also not "Mozilla-controlled". It's a feature that will, in the future, come with sensible defaults, just as uBlock does with their default blocklists, but in 116 the user will be able to more fully configure the feature. Meanwhile, in 115 the feature isn't active by default because the extension whitelist and domain list are empty.

How do they know what sites I consider sensitive?

How do they establish trust for an extension?

How many dollars do you want to wager that they are building this feature with the intent to get sued so that they can be forced by the courts to turn it on for sites like youtube?

> How many dollars do you want to wager that they are building this feature with the intent to get sued so that they can be forced by the courts to turn it on for sites like youtube?

Good god, the conspiracy theories are next level with this one...

Ah, I get it. Thank you.

> It's also not "Mozilla-controlled".

It's not? The bugzilla entry at https://bugzilla.mozilla.org/show_bug.cgi?id=1832791 says

    We need to have ability to set the list of 
    quarantined domains remotely.

Which sounds pretty Mozilla-controlled to me. I hope that Mozilla will allow reasonable user control over all of this. I'm aware of their stated plans, but until we don't know what will be until they actually implement them.