With traditional adult entertainment, creators are aware of the social ramifications (e.g., social stigma, familial ostracism, difficulty dealing with the future, and so on), and there is a decent theoretical economic framework to measure that.
I am not sure if there's the same this new army of "civilians" joining OF, let alone the additional toll it will take on the creators in terms of social ostracism, future prospects, future opportunities, and mental health.
How is that 'fine'?
I would like to see a future where someone doing sex work to make ends meet (or even as a freely chosen profession!) is not ostracised for it. Sex is part of society whether you want it or not, and so is paying for sexual acts.
Some cultural norms are outdated, but prostitution is still degrading and dangerous for those practicing it, especially for the women; who may not be doing so willingly, prostitution being the main incentive for human trafficking. And the online medium doesn't change that by much.
Some people may be willing to pay for sex, some people are willing to pay for many other things or activities that should be or are illegal.
Consider the sex workers who deal with mentally or physically disabled adults. Most people have sexual urges, and those who are unable to participate in society in the usual way of addressing their urges with a romantic partner or a one-night stand still have them. There are a good number of very professional sex workers out there who can provide these people with sex (often with specific expertise for the relevant handicaps) and generally significantly improve the wellbeing.
Are those sex workers doing something they shouldn't be doing?
You are asking a binary question for which there isn't a binary answer. Better to ask are those sex workers doing something they will get a pat on their backs for from other members of society? In a way a builder, chef, firefighter, and even a prison guard would.