Instead of regular centralize stablecoins, why we don't have a stablecoin with its own blockchain or a token where anyone can mint or redeem that stablecoin using ONLY Cryptocurrencies at the market price.

For example if I have 1 Eth and want to mint it into Xusd (community stablecoin) it goes like this example:

If Eth market price = $1000 I send 1 Eth to this blockchain or contract and I receive 1000 Xusd.
And it can be redeem for any Crypto at market price,
If Eth price = $2000 I send 1000 Xusd and get 0.5 Eth.