so far so many Dapp developers have made so many Dapps which are integrated with MetaMask or other similar extensions like Parity and Web3.js.
Is there any idea or suggestion about developing one without all those extensions mentioned above ?
Thank you.
There are mostly two reasons these extensions exist:
The user shouldn't need to trust the website to provide their. blockchain data source, and more importantly, users should never have to trust a web app with their account's private key.
Of course you can make sites without those guarantees, but to do that kind of misses the point of decentralizing trust.