I think the reason many people prefer VNs is that it's much more difficult to make a good sandbox game. Beyond the story and characters, you've also got to figure out the GUI (locations, navigation, stats display, etc.), what stats are available and important (I've played too many adult games where you spent more time managing your health, hygiene, hunger etc than you do romancing/seducing/corrupting the LIs. That's really not fun), what times of day are available(ideally once you're past the early game there should not be a time when you're skipping), whether or not an inventory is important, where are the NPC characters at what time of day, and most important (to me) what kind of hints do you give the player to help them move the story forward. Because of this, most sandboxes are executed poorly.
This sandbox is better than most but it still has its warts. However, that doesn't mean that sandboxes are bad in general, just that significantly more care needs to be put into designing them.