In some cases, the problem is just that the free market sets up a race to the bottom and regulations can provide an artificial bottom. This is the standard argument for the minimum wage, for instance: even if businesses can afford to pay more and still be profitable, they won't voluntarily do so in a market where there's more supply of labor than demand for it.
In some cases, like livestreaming your hotel stay or selling your organs or sacrificing your lungs to mine coal, there's a qualitative difference, and saying "This job no longer exists" doesn't solve problems. If that's the case, society should figure out if it can afford in any way to provide for people's basic needs so that they can start having meaningful other options.
It seems entirely possible to me that a society with a strong social safety net (welfare, UBI, whatever) needs less regulation of its free market than one that puts the burden on its market to treat the most desperate in society with fairness.
(BTW, a minor point about sex work: I believe "legalization" refers to making it a regulated industry with the remaining possibility of criminal penalties for breaking regulations, and many sex workers prefer "decriminalization," i.e. just removing criminal penalties.)