This has nothing to do with block size, but is an inherent property of PoW and economies of scale.  It is true that bigger blocks would push a bit faster to optimise the network topology to the reality of the client server nature of bitcoin but this is inverting cause and effect.  The network topology is not the cause of centralization, but its effect.  The real centralisation is the fact that only a few entities produce the data, the block chain.  The network only adapts to that reality but is not its cause.  PoW with specialized hardware and the economies of scale automatically lead to a few central mining centres.   That is not the block size or the network that push to that, it is the economies of scale in PoW and the smoothing out of the "lottery" (instead of winning once a whole block per year (or not), you prefer to have regular income with a pool).

This whole debate is misguided.  Block size has not much to do with it.  The real centralization is the fact that only 5 entities have majority hash power (and hash power is voting power in a PoW system), and that 14 entities have almost all hash power.  This is already the case.  The ILLUSION that the nodes are manifold, while they are only CLIENTS DOWNLOADING DATA from these 14 data centres through their proxies in the P2P network gives you the illusion that bitcoin is not centralized.  So this whole debate is simply about keeping up an illusion of decentralization by avoiding the network to adapt to the reality of the data flow.