What are you talking about? Opera and Mozilla are both in the business of trying to deliver a good browser, which means good features. Different financing doesn't change the mandate to deliver good browser features, and Opera most definitely did rely on search licensing as their primary income stream anyway, despite attempts to diversify (for years they relied on Google and Yandex and got more money from that than other forms of financing).

As I said, my opinionated hot take is that Opera was probably the best ever at delivering features and performance beloved by users, but that wasn't enough to move the needle on market share, which is why Opera perfectly exposes the fallacy of assuming better features = better market share. In this context appealing to "business structure" is a deflection.

Also, this tab grouping argument is mistaken both on its own terms but more broadly as a stand in for the argument that the Mozilla team has supposedly done nothing. Firefox had native tab grouping years before Chrome ever had it, had arguably the best tab grouping extension of any browser due to an intentional choice to invest in an extension ecosystem that made that functionality possible, and for the most part, Firefox has never not had tab grouping. What's new is that it's back as a baked-in default rather than merely present as a best in class extension.

The idea that Firefox has done nothing is an unfortunate impression that comes from looking at a serious of unfortunately critical tech headlines and losing sight of nuts and bolts development. I don't have the patience to recite everything here, but every year they push millions of lines of new code, thousands of patches, and deliver measurable improvements to major browser components like webGPU, javascript rendering, shipping production quality rust code, and more for a browser with 30 million lines of code.