I don't think this is about introversion, it's about comfort zone and the fact that distribution is really REALLY hard, especially in a crowded market. If you're a builder, it's easy to stop the hard thing, which can often be super unfulfilling and feel like banging your head against the wall, and slip back into your comfort zone of building stuff.
Thing is, it's never going to get easy. Your product is never ever going to sell itself. Building a public profile, content marketing, etc. is one affordable way to get the word out. The other way is word of mouth. Both of those require you to get out there.
All that being said, I'm firmly convinced the MVP culture of launching as soon as you've built a UI with Bootstrap and thrown it up on Heroku is bonkers. Take some pride and ship something good (which it looks like you've done).