But posting Rust as a product and claiming FireFox is not successful is simply not on the level.
FireFox has been amazingly resilient given the onslaught aimed at it, the fact that it still has the marketshare it does is a success in its own right. That that marketshare is dwindling should surprise noone, least of all those working at Mozilla.
As for your experience: that is how most products are developed. But Mozilla is not - at present - a company with more than one successful product. Not from my perspective, and likely not from any of the other frequent users of its flagship product.