Isn't this the same as what we all do, just more anonymous? Like, you can't pay for housing unless you show up to a place owned by someone with 3 yachts for 40 hours every week. While you're there, you can't listen to music or visit certain websites. If someone coughs on you and you get sick, too bad. You also can't use your brain for things work-related outside of work hours; all of your ideas are owned by the crazy yacht guy! If you want to work for some other yacht owner, then you have to take a day off of work and write code on a whiteboard in just the right way.
All of this seems significantly more degrading than selling a naked picture of yourself. The OnlyFans models are selling their body, but you are selling your mind. That's what really makes you you!
I don't really feel this bad about work, but at the end of the day, I don't consider myself engaged in a pursuit any more noble than selling my time to the highest bidder. I can see how parasocial relationships seem weird, and personally I have zero interest in them, but it's quite a stretch to brand anyone involved with one as "mentally unstable". What if they're stable and they want to spend their money on that instead of a $1500 phone, or a $60,000 truck, or a $200 dinner with their friends? I'm not sure any of us are all that mentally stable. Rather, we get by.