Marketing is 90% of the Work
Regardless of whether you created a digital product, an app, a web app, or a service, if you don't know how to market it and how to market it properly, it's going to fail.
Even if you create something that is the best on the market out there and, on top of that, is cheaper than everyone else, still, if you don't know how to market it properly, no amount of word of mouth marketing will help you.
Don't start creating anything if you don't have a marketing plan, especially a good one, and if you're a beginner, I'd recommend you just copycat the marketing of someone you find in your niche that is already successful.