My point is rather that an online marketplace in the absence of decriminalization and reform can only provide a marginal increase in safety. Sex workers marketing on Backpage, Craigslist, Onlyfans, and IG still face a great deal of risk of violence, pressure from pimps, and prosecution by law enforcement. It's a deeply complex systematic issue which can't be fixed by a website.
For drugs in particular, darknet marketplaces primarily rely on unspeakably violent criminal enterprises upstream. The consumers, sellers, and communities implicated in this supply chain are all losers in this system. The cartels are the winners and the global "war on drugs" establishment are a close second place.
Still, in the case of sex work, I think you are simply wrong. Your overall sketch is the "movie version" or police/puritanical version of sex work, a version that equates trafficking and voluntary transactions (not that those transactions can't exploitative in other ways). The majority sex work isn't filled with violence except on the level of the literal street. Notably, my friends and acquaintances who used Craigslist back in the day didn't deal with any pimps and a moment's thought would show pimps are only needed when someone sells sex at a physical location.
Also, afaik, onlyfans is a virtual only platform so workers there face the same physical dangers as people on zoom calls.
Drugs is a more complex beast.
Pimps are needed whenever there is coercion involved. It seems unlikely to me that only street prostitution requires coercion. I think we'll soon learn that most of the women on OnlyFans are there because of a violent and manipulative man.
But yes, it can and does happen. Any system offering freedom can offer just as much freedom to those who coerce others.