Google isn't a "steward" of anything. They are an entity concerned with expanding their own power. And there is absolutely nothing that you, or I, or any other browser maker, can do about it.

But at the very least, we can be honest. If Mozilla published a blog post today that said something like "While we are ideologically opposed to WebEnvironmentIntegrity, we will almost certainly be forced to implement it in Firefox eventually", my respect for them would rise tremendously.

Firefox has lost. There is no shame in admitting it. But there is shame in pretending it isn't so.