Firefox got popular when they listened to users and made a product people wanted.
They did this despite fierce competition from a huge monopolistic company with quite a locked in and anticompetitive platform.
And today they make something crazy like a half billion dollars a year from firefox, they have enough resources to make a competitive browser.
Also, they still make a competetive browser, as I laid out. Just the fact that some of the competition has improved massively (but by no means all of it) doesn't change that.
Competition has improved but so has firefox. Why should the expectation be that they stood still while everybody else went ahead? And it absolutely has declined. You also did say that they don't have features you want and seemed to imply that was part of the realities of not having enough resources or struggling to compete with google. Just doesn't seem like the reason holds water.
They certainly listened to their users and potential users.