Mere exposure
Repeated exposure to something increases preference for it, with no argument required and often without the person noticing. It is one of the more replicated findings in social psychology. It also means preference is accumulated over time — which a single-day launch has no mechanism to produce.
The launch-day problem
A launch is a moment. Memory is built by repetition. So the post on the day reaches people with no prior exposure, at the one moment you need them to act, and the silence gets read as “the market didn’t want it” rather than “the market had never heard of it”.
Distribution is a design decision
Name the specific publications, communities and people while you are still building. If you can’t name them during the build, you won’t conjure them the week you ship.
The unglamorous version works
Direct messages to people who would genuinely care. An email to everyone who ever enquired. Three conversations with people who cover this. It doesn’t scale, and it beats a post into an empty room.