It is sometimes difficult to tell if some artworks were decorative, religious or both. I'm really not an art historian, but I can offer some guide lines.

A fresco in a Roman villa is probably decorative. But when you see statues? It becomes hard to tell. We don't always know. And I said that it could be both, because it may have been. Roman religion is not an organized religion like Christianity. There are temple sure, when we find fragments from altars we know it's for religious purposes. But when a rich man orders the crafting of a statue... is it purely aesthetics? Or is he a devout follower that want to honor the goddess? We do not know.

It's also important to understand that since it wasn't an organized religion, different people had different interpretation of what the goddess meant. Sometimes she was Venus the goddess of physical love (there's a reason why we call aphrodisiacs aphrodisiacs...), but at times she was also Venus Genitrix, Venus the mother (this one is thought to be a religious statue of her), Venus Felix the goddess of luck. In Pompei she is often represented in full dress and with jewels.

But my point is... if she is presented nude (like the many many nude Venus you can find)... it doesn't mean it's lewd art for the male gaze. She is a goddess (nudity is associated in antiquity with gods), she is also a goddess of sex. Her beauty doesn't imply that it's lesser. Those statues aren't the ancient equivalent of Playboy.