Just because they renewed the look does not mean that Firefox is doing very well. The entire research industry was fired. Firefox in the future will be stagnant and will be swept away by Chrome. But I'm sure the community will raise another titan to fight Google's ills.
Firefox's market share is already a rounding error. A change in focus to the browser (not saying that this is what's happening) could be nothing but an improvement or a no-op.
Is this irony? A lot of the fired developers worked on the engine and all the surrounding levels below the UI, there are bugs lasting years in the current engine, but this is the UI lipstick change nobody needed anyway but its convenient for the management to demonstrate that "they" did "something".
A tab that doesn't look like a tab but like a button. Progress!
Thankfully that doesn’t seem to be the case!