Ask HN: How to become good enough in UX to sell your apps?

I am constantly developing little web applications and became very good in a basic Full Stack environment with JavaScript and some database. Good enough to serve to a few hundred customers, fix bugs etc. I am a full time JavaScript developer, and what I am lacking are the skills for a good enough design to present my apps to a broader audience or investors. Also, UX/Design plays a huge role in if customers pay for a service or not (in my opinion). There are many books and courses out there, and I am kind of lost. So, does anybody have tips of how to get started to polish web applications to a good enough design to go public?