What's the one thing that contributes to a successful product launch?

Iterating on feedback. It is most likely that your MVP won't be perfect, so be open to feedback during the launch. Use user recording tools like Smartlook Qualitative Analytics to check how people interact with your product, and make sure your onboarding flow is OK. Besides this you can check out my Product Launch Action Template for other tips.

Build your waitlist long before the launch date

There are many factors that can contribute to a successful product launch, but some of the most important include having a well-defined target market and value proposition, building anticipation and buzz around the product, ensuring that the product is of high quality and meets the needs of the target market, and having a solid marketing and distribution plan in place. Other factors that can contribute to a successful product launch include having a strong brand, effective pricing strategy, and excellent customer service. Ultimately, the key to a successful product launch is to thoroughly plan and execute every aspect of the launch, from product development and testing to marketing and sales.

If you base your success on upvotes, you are gonna end up with a surprise. Nobody knows if the upvotes are converting to actual free/paid users or active members within your own platform. I couldn't find this type of information anywhere yet. Like what Joan Mateo Duarte mentioned, Networking and I would add being aggressive about it. But to me, that ain't it. You can try to post a topic on the type of product you plan to launch and see if it picks anyone's interest. Try to provide as much material as possible to convey a clear message on what the tool does and why it would make a difference. That's about it, IMHO. Best of luck!

Networking is by far the best.