For quick user feedback, maybe give the product away for free in exchange for testimonials. Reach out to friends and family. Implement the changes they suggest. Once you have some solid testimonials built up, you can raise the price of the product. Rinse and repeat. I recommend watching some Alex Hormozi videos on how to effectively market and sell.
But where can I get the initial traffic? I don't even have any early users right now.
2) I hear that you scratched your own itch. When you had the itch/problem, what did you do to see if someone else had solved it before you started building? If you “only” did a quick google search, then you can try to rank for the phrase you searched for (which might be super hard). Did you post on Reddit/slack-group - if so, build a presence there so that when other people ask that same question, you can be there to help (and mention your solution)
3) try to meet people in real life who might have this same itch/problem, and talk to them