It's worth remembering that Firefox HAD tab groups before, just under a different name and then killed it because "nobody used it": https://medium.com/@twidi/how-i-survived-the-removal-of-pano... The implementation here is a bit different, I'm sure, but the core idea is the same: Group your tabs however you like and switch between the groups at will. I use Vivaldi these days (thanks to it's excellent UI customization…
I guess there probably are features that can be trimmed back, that go unnoticed and don't draw attention.
But sometimes I think companies refactor something and just don't want to think about supporting something. Or, they have an unpopular hidden motive.
(I think of apple's target disk mode, and tesla's non-existent dashboard and now turn signal/drive select stalks)