There are couples looking for other couples or thirds, there is the BDSM scene with people looking for casual play partners, and so on.
Just sort of overall, when your interest is in building a network, finding people to have casual sex/encounters with, a "stream of people to meet" as someone mentioned below, I think you'd want a different website/UI than these big dating sites seem to offer/encourage. That said, I've never used them, just speculating based on the ads I've seen over the years and how they paint themselves.
many users of that kind of profile are just outsourcing actual human interaction to dating apps that claim to solve it but are incapable of doing so
While there are specific sites for BDSM dating with more nuanced optoins, the ads for generic dating sites are all very "tame" and try to not deviate from the perceived norm too much (= "find a partner, have a happy family" type messaging)
The reason is that if you do, it's virtually impossible to get included in Ad networks and App Stores. So you naturally see only dating ads catering to the very conservative viewer.
Example: A BDSM dating site got banned from Googles Play Store after including a background image of a simple leather whip. [1]
[1] https://twitter.com/devianceapp/status/1384015666185834501