Power users love to bash accessibility features like this. Its a classic case of “I don’t need a wheelchair ramp so i dont know why the library added one!”
Accessibility is way more than screen readers. It’s more than specific disability-minded modes. The web needs to be friendly to everyone, including people who may not know they could benefit from accessibility features. Everyone benefits from this type of work.
There are definitely some legit feature concerns and priorities being called out here. Mozilla has left a lot to be desired of late on that front. But a power user is more than capable of jumping into settings or about:config to turn things like this off, or finding an extension to get by for now.
Also the firefox dev team isn’t tiny. This isn’t blocking other work or anything in a substantial way, it’s a fairly isolated piece of UI, and there’s no guarantee that skipping this would change the timeline on anything else.