Why do you care?
I mean that seriously. Sometimes when one asks a question the asking may be more insightful to you than the answer.
I mean, you'll get a bunch of answers here, reflecting a bunch of opinions. But why do you care about what they think? And what does it matter to you what Zuck is or not.
It doesn't sound like you're asking about billionaires in general (or the number of them, or the harm they are doing), and you're not asking about Facebook in general, but rather on Zuck himself.
Do you think the success of a person is based on their original ideas? Or is it on execution? Do you think he's a bad CEO because his company (and him) are visible? (Does your local accounting firm with 10 employees get the same scrutiny?)
Do you think a CEO operates in a vacuum? Is he the only one eith ideas? Is the the only one (inside meta) who makes bets, or buys companies?
All of which brings us back to, why do you care? Is your success delineated by his reputation? (Hey, maybe you're C level at meta aiming for his job.)
Honestly, I've found for me, caring about the success, or deservingness, of others (big or small) is meaningless to me. Their success doesn't make me fail. Their moral failings doesn't make me a success. My job is to be the best I can be, not compare myself to others. And my definition of success is what I want it to be, not some measure society offers (like absolute wealth.)
I'm objectively a bad golfer (outside the top 100 000 in my country, as my phone delights in telling me), but my measure for golfing success is how much fun I'm having. I don't hate on Rory for his success.