In theory you should be able to build a new NFT marketplace and airdrop the shit out of it to replace OpenSea.
The reality however is that market dynamics, acquisition costs, network effects etc prevent this from happening. And these aren't things that crypto can really solve.
[1] https://www.theopendao.com/ [2] https://decrypt.co/89325/sos-token-aidrop-opendao-opensea-wh...