Marketing is a VERY different skill from building, and can take years to master. As someone who has built several side projects that landed in the "didn't make any money" bucket, it's easy to fall for the "build it and they will come" mental trap. I am starting the journey of learning marketing now, but I have a lot of optimism, as I am learning all sorts of things that don't work, and looking forward to trying the things that people say do work.
One thing that helped me was when I was full time at Automattic, I intentionally started using my engineering skills to help the marketing team, and eventually was able to switch completely over to the marketing team to help with landing pages, analytics, attribution, data, etc. I was able to learn a lot about marketing through that experience and it helped me get a lot more savvy about it for Preceden (though it still doesn't come naturally to me). You don't have to go that route though - the Microconf videos are excellent sources of marketing advice - but if you can immerse yourself in that world in your full time job, it will go a long way.
Love the advice! I made a targeted team move last year to help my side project, but didn't even consider marketing. I might have to see whats available.