Besides being a overall good lighthearted game and developer Braindrop being a cool guy.
In WVM, one major thing that kept me coming back is that WVM has a True Harem story with the MC and girls being in an actual polyamorous/polygamous relationship and it’s one of the story’s main subplots. Along with that, finally a Male MC that's portrayed competently and level-headed with a backstory of being successful at something and with a promising future going ahead for him, and is popular based on his merits.
Personally, I'm tired of same setup of games kicking-off the story with a plain MC who's boring life is drastically changed by various reasons, then surrounded by multiple women. In most visual novel games here are either “one girl only per route” type or “you can bang them all, but must pick one towards the ending” type to get a good ending or get game over. You'd be lucky to get a three-way romance ending, if the developer is feeling generous enough. Those type likely treat a harem (3+ girls) as a little bonus ending, not its own story path + ending. Other games i know of with a confirmed actual harem story path are "Sisterly Lust" and "Parental Love".
I'm a simple man, give me a real true harem with a competent & strong MC, then i'm hooked. Be in Anime/Manga/Visual Novels/Western Erotic Games & Comics.
Plus the story's overall wholesomeness and variety of women. I like how the relationship dynamic is almost set-up as "Peace & Love within the inner circle of the MC & his Girls" vs the "drama & disruption caused from outside of the group". Also, for Braindrop not bothering his players with the vague "choices might have dire consequences reminder" that some games do.