That's why I think Bitcoin is outdated (yes, get your pitchforks), and you really need something that can do smart contracts.

Bitcoin you can hold it, transfer it, and not much more. Having smart contracts (like Ethereum) allows you to have something like Uniswap, which is decentralized and allows you to trade your coins.

Yes, it's not a fiat on/offramp, but if stablecoins are actually good and backed, in the scenarios you describe you would just buy/sell stablecoins and at a later point exchange those stables for cash.