20/30% market share is a massive win for an ethically-led company in a market dominated by the richest companies in the world (literally).
They don’t need 51% and never will. What Mozilla needs is a solid 15/20% to buy a seat at the tables that matter (standards etc).
Btw, if iOS allowed any other browser, Safari’s numbers would go way down almost immediately. Way.
Chrome and Safari are much stronger competitors than Internet Explorer was then, so its understandable why Firefox is struggling. Being locked out of iOS doesn't help either, though I'm not sure it would make much of a difference even if they weren't.