OP, mining is cartelized towards the biggest mining farms, but the network itself is still decentralized/censorship resistant, thanks to the people around the world who continue to run/maintain their full nodes. More full nodes = more security.
This I guess was my point - there's this "cartel" of big mines that effectively verify all the money. Those full nodes just keep a record of it. So there's still a small number of entities (these large mines) that have the control over bitcoin's transfer. You can't send or receive bitcoin unless one of these big mines agrees that you did by putting it in a block. If they all went away yes the small miners would pick up the slack, but odds are (statistically speaking) it's one of these few big mines verifying everything.
We've repeated the same mistakes already made with the rest of the economy. Walmart killed the local stores. Chain restaurants killed the local cafes. Big mines killed the ability to mine.