Mining crypro doesn't materialize money. You have to exchange it for real money which means taking a private individual's money in exchange for scam tokens.
This is the problem crypto fans refuse to acknowledge. The money doesn't magically appear, you're taking it from someone else and letting them hold the bag when whatever cryptocurrency you choose inevitably blows up, fails, or rug-pulls. It's unethical to engage with at all because you're still participating in scamming real money out of private individuals
Not necessarily. You can spend your cryptocoins with any number of businesses and it is very much the choice of those businesses to accept them or not. No private individuals need be involved.
Note also that any non-crypto currency can also devalue at any moment, although perhaps not to the same extent. Holding anything of any perceived value carries a risk and also a potential reward.