I think, my and your definition of web3 is different. In my definition web3 is the democratic web. Technologically it can be a blockchain, a blockchain-based DAO, or (as I wrote) a simple web2 like app with a democratic government structure. It doesn't need complex architecture. Complexity depends on the trustlessness of the system. If the members are identified and trusted the system can be simple (ex.: a PoA architecture). If they are unknown and untrusted then you need a more complex system like PoS that has a minimal carbon footprint or PoW that has a large carbon footprint.