I feel like you could have said the same thing about IE 4.0. It's more like, the incumbents don't care outside of what they need for their own purposes and Mozilla is the one supposed to be doing it but they're not.
> Unlikely you'll gain traction among regular users who are bagged to use their OS or search vendor's own.
Chrome has 64% market share on desktop despite the proprietors of Edge and Safari having a combined ~90% desktop market share.
> Perhaps one could gain Mozilla users, though hard to compete against millions of dollars of development (regardless of whether CEO is taking a chunk or not).
The problem is more than the CEO taking too much. They're not actually spending most of the money on making Firefox better.
They should also be spending more of it on marketing, because their funding is directly tied to how many users they have, which keeps going down.
Find some existing pain point that people don't like about Firefox, fix it, make sure people know the better version is available. People switch to it, you get more search revenue and donations, you hire more developers. It's the same way Mozilla operates, but this time you hire competent management so your market share goes up instead of down.