Think of it in terms of video games. Soft-launch is like an Early Access game. It’s very explicitly not feature complete, lacks the refinement of a finished product, and exists as a kind of crowdsourced quality assurance tool to figure out what works, what doesn’t, and gauge the opinion of people who aren’t professional developers who may have biases and blind spots as someone who understands the product at a deep level. A soft launch usually has minimal if any marketing done, and explicitly targets people with special interest in the product, while the hard launch is the polished final product and gets a much wider marketing push.