For me, I don't view it as acid burns through flesh or anything gruesome, it's more like slowly, softly becoming part of what eats the protagonist, softly as in feels good, and feels better the more you give in and accept your fate. Plus, there is the appeal of fleshy walls caressing and massaging the body everywhere. The game over is not like actual death, more like falling asleep in a cosy warm bed, like your consciousness fades away, but it does not feel bad. Part of the appeal is the prey being secretly into it and her being into it gets her in even more helpless situation until she completely gives into her hidden appeal for being eaten.
I know it's certainly not for everyone, but I think it's nice to show people who aren't into it a different perspective, on how it can be enjoyable so that it might not look so odd. I hoped this helped you see it under another angle.
