Web3 Data Storage

No it's not efficient or necessary to store everything in the blockchain and that's where off-chain storage comes in. As in some cases data might be too large to store on the blockchain. So, it might need to be modified or deleted which is not possible in a blockchain where all the data is read only.
The most common solution is the interplanetary file system or IPFS. It's a decentralized way to share files very similar to the way bittorrent works. And there's also databases built on top of ipfs like orbitdb and threaddb.

E.g. Peeranha stores all the data on Polygon blockchain and IPFS/Filecoin. You can find "Source" button to see how does it works.