"not necessarily pretty smart" is a very nice way of putting it.
I don't know where the threshold ought to be, but beyond a certain size a pile of money can only indicate bad things about its owner. Either they're too unimaginative to turn that potential into action, or their designs are so against the will of the people that it's going to take gargantuan amounts of coercion to get them done. Either way, a billionaire is an individual of dubious merit.
> Either way, a billionaire is an individual of dubious merit.
This sounds like the "poverty is a moral failing" argument in reverse. See eg https://unherd.com/2017/08/remembering-time-poverty-often-bl...
Most rich people aren't sitting on piles of cash; their capital is (usually) invested in a corporation which is busy turning potential into action, as you put it. I think there's an argument to be made that amassing and hoarding great wealth, particularly near the end of one's life with the intent to pass it directly onto one's heirs, is morally questionable if you believe in any kind of universalist ethic. But I think criticizing someone as uncreative simply because they're not selling off all their equity to go pursue some other venture is way off