The current system where every user is a network node is not the intended configuration for large scale. That would be like every Usenet user runs their own NNTP server. The design supports letting users just be users. The more burden it is to run a node, the fewer nodes there will be. Those few nodes will be big server farms. The rest will be client nodes that only do transactions and don't generate.
That is users vs nodes, not nodes vs miners.
As you pointed out, the nodes and generators were the same at the time of
that quote. So you can't say that it applies only to the miner side of them.
When it says, "client nodes that only do transactions and don't generate"
I don't think it applies to full nodes, but wallets.