IMO, Facebook isn't a finished product. The product changes in ways that are hopefully useful to the majority of users over time. It isn't always possible [and it isn't simple, and it adds complexity, and bugs, and it doesn't make sense] to maintain every feature that once existed -- the product would stagnate if we tried to do that.
BUT what it seems that Facebook is lacking is a clear sense of direction when it comes to providing a platform that is accessible yet robust, interactive yet intuitive.
Your conjecture that the product changes in ways that are useful to the majority is a conjecture I refuse to buy because if you were to actually give your user base a chance, give them a voice and poll them, I'll bet my salary for the year 80% of them (techies and non-techies alike) will agree that Facebook has degraded to the point of being almost useless.
As for your bet, the obvious counterargument is that 400 million users still visit the site every month, and I haven't seen any signs that that graph is even slowing down. Isn't that a more convincing statement than a poll or a forum with very vocal techies?
Convincing is when you're able to build a platform and assimilate naturally evolving elements of what makes that platform great, and the community that exists on top of that platform to enhance the experience.
Interestingly enough: your prime competitor has done this exceptionally well.
Do you know who I'm talking about? Of course you do. I'm talking about Twitter. In fact, they've done it one hundred times better than your employer has.