Facebook is one of the most successful companies in the last 10 years by any possible metric. The fact that you like it or not doesn't change whether it's successful or not.
All of these things have made Facebook a lot of money but there is definitely an argument to be made that Facebook has decreased the Gross National Happiness[1] of both the US and the world in general.
Personally I'm not a fan of Facebook, as I saw my home city (Budapest) becoming from a nice livable city to a tourist destination / loud party / get drunk fast city between 2008 and 2010 (and it hasn't gone back), and I believe Facebook took part in that (of course later AirBnB helped, but AirBnB was much smaller in that point).
As for other effects, like making people less connected in real life, and more through computers, it has good and bad side effects, I'm torn whether things got better or worse. (Also I don't post too often to Facebook, so I'm not a good person to judge it).
>It's pretty successful at decreasing the happiness of people who use it.
this? Because unhappiness and facebook use is obviously going to correlate for reasons that have nothing to do with facebook being bad, and I think Facebook is a valuable enough tool for maintaining relationships that I'm skeptical it would outright decrease happiness (on the individual level. Society as a whole I find much more plausible).
So..you imagined a few metrics and wrote "any possible metric"? Ok, so you were exaggerating..
I will try to imagine some metrics FB may not be the most successful in: companies that did the least evil, percentage of users that unreservedly loved the product, percentage of users that felt exploited, percentage of users that felt the product was better than 10 years previously, percentage of users that trusted the product, etc.