Some types of stories absolutely have a minimum (and maximum) length. For example, the Odyssey is the story of one man’s very long and eventful trip home. The emotional payoff of him actually getting home only works as a payoff because of how long it took to get there. The length is the whole point of the story. You can condense the plot to a haiku by summarizing, but it’ll lose all of its emotional impact. So, your concern is a valid one.
That said, it very much depends on the specifics of your work. You don’t need general platitudes about how it’s OK to write a short visual novel, you need specific feedback about if your visual novel works at its current length. Read it yourself while pretending someone else had written it. Get your friends and family to read it. Post your visual novel in Get Feedback. Take it to a local or online writing circle. The only opinions that matter are those of people who have actually read it.
I can very much understand not wanting to let people see your unfinished works, but you either need to push aside that feeling and find someone you can trust with your unfinished work, or you need to completely rely on your own judgement. There is no third way.