I don't know about "just as much". Negatives like these are hard to quantify and therefore hard to compare. What the men are paying for on OnlyFans is a pseudo-connection or a fake relationship. This strikes me as being emotionally, sexually, or romantically manipulative or exploitative.

Of course the men choose to contribute but the incentive structure is for the women to foster a sense of intimacy or connection so they can exploit it for cash. It's a voluntary association, but it doesn't seem like a morally neutral or harmless association to me.

This is not to say that the harm men face from exploitation is greater than the harm that women face - or that women don't also face this phenomenon, but just that it is also a harmful byproduct of the service.

I think what was meant is a belief that porn addiction causes brain damage (to the addict).