If you look at them on an individual basis, of course none of them passes the decentralized test
The "of course" will be disproven.
I understand your point is you think competing altcoins is a form of decentralization. But if all of them are not decentralized, then no matter which one you switch to, then you've still got the same "light bulb" (from your analogy) in control.
The wealthy can spread their wealth around to all the important altcoins as well.
The problem isn't solved in your conceptualization. Sorry.