I think we agree that the block size should be a function of the resources requirement for one person to become a peer in the network (fully validate by running a full node).
Therefore it stands to reason that the Bitcoin blockchain will forever be able to accommodate only a marginal amount of transactions worldwide given the resources load implied. Hence the exclusive, "luxury" qualitative.
In which case, we need a definition for the size/location of the margin. I suspect that outright exclusivity is only one way out of many.