Pretty much all of those forks are small volunteer projects that rely on upstream work by Mozilla, who are already struggling to keep up with MS, Google, and Apple. We were already at a point where Mozilla was laying off technical staff a few years ago. We're now seeing sites just outright block Firefox because it's not worth the effort when most users are reaching for something built atop Cr. How would any of these forks survive?
The worst that would happen is that the forks don't stay updated. They won't stop working. It's pretty easy to evade the blocks on sites that are poorly designed/managed enough that they feel it's necessary to block certain browsers.
>The worst that would happen is that the forks don't stay updated.
Which is hardly trivial, there are hundreds of open issues on Bugzilla for XUL alone. Some of the gaps include accessibility issues, which is down more to Cr better supporting APIs provided by vendors like NVDA. This is first of all, not something that is 'easy to evade' for the affected demographic, and secondly something Mozilla was an industry leader in for a long time. Obviously, Google didn't invest in this out of any sense of altruism, but it speaks to the sustainability of browser development, and what approaches thereof actually work.