Sure; a DAO is just a corp that has smart contracts. There is no web3 thing. I feel very dehyped about the space and still like it though, not sure who actually likes OpenSea among diehard NFT folks. You also don't need to use their smart contract
Be the change you want to see and that, maybe I'll be able to find something to make that isn't just apes and punks
Yes, OpenSea is centralized. That's part of the hype around SOS as an alternative, creating a decentralized NFT exchange instead.
Content hosting is also centralized (ie on Google Drive or at a URL).
NFTs can be decentralized. Current versions are not. The files are not stored on a chain or via IPFS. And there's no decentralized exchange.
The current version is kinda like an MVP stitched together.