The resource usage of blocks is limited by the programming of the system. This is necessary because we live in a physical world where resources have costs and Bitcoin's security depends on participation being widespread so the costs can't be too great, along with other reasons.
You very well know that this is not true. Bitcoin's security depends on proof of work, and the decentralization of those providing it. Period. Bitcoin has a proof-of-work consensus, meaning,
the consensus decisions (ALL decisions) in bitcoin are taken SOLELY by proof of work (mining). Nobody else can decide anything else cryptographically/technically in bitcoin, not any "majority of full nodes" (too easy to Sybil) and bitcoin chose not to be a proof of stake coin, so stake holders have no cryptographic/technical decision power either.
Of course, bitcoin being a value-token, the other power in the system is the economic one, which is given by people who buy and sell coins in the market. They determine market value. But the decisions in bitcoin, on which its security depends, are taken solely by proof of work, and that was designed that way on purpose. So no non-mining entity contributes what so ever to any decision or security in the system. I'm not saying whether this is good or bad, I'm saying that this is the way the system was designed, and is working.
The resource usage by proof of work is many, many orders of magnitude larger than any other form of practical resource usage in bitcoin, and that's by design too. So if you can waste all the resources needed for proof of work, you can always use the very insignificantly small additional resources to keep the network running.