Stellar is not centralized. Anyone can spin up a node. Any node can be a validator node.

You may be confusing Stellar's technology with Ripple's -- Ripple is definitely centralized.

It's a web of trust with its federation servers. Reliance on large trusted third parties meets my definition of centralized. The economic majority will be highly vulnerable to regulatory pressure, due to trust collation. That regulated exchanges are part of the protocol makes the likelihood that the economic centre will successfully resist regulatory pressure even less likely.