You’re saying this like Firefox is adding the shitty standard because they want to, and not because Google used their monopoly to force adoption of the shitty standard forcing Firefox to follow suit if they don’t want their users to have a broken experience.
If Google introduces a shitty standard to YouTube and Firefox doesn’t adopt it, do you honestly think users are going to care or understand and blame Google? No, they’ll get pissed because they think Firefox broke YouTube and they’ll move to Chrome.
This exact situation played out with shadow DOM, Google implemented it into YouTube while it was still a draft standard, so all non-Chrome browsers ran worse because they had to use a polyfill.
That is why we’re telling people to stop using Chromium. If they didn’t have this monopoly none of this would be possible. Mozilla has some issues as an organization, but do honestly you think the better choice is letting an advertising company decide how the web works?