Users think they know what they want, but you get the horseless carriage effect where you're getting asked for a faster horse.
You have this idea that you think is awesome. You want to have that broadest group you possibly can. You don't want to just talk to 1 type of person and learn that, you want to get familiar with the space.
That's actually one of the most disappointing things about doing user interviews and user feedback, which is why I think... people don't do it. You're going to get negative news about your favorite pet feature most of the time.
The other mistake I think people make is talking to who's available rather than talking to who they need to talk to.
I wish I could tell you the recipe for figuring out who the target user is for your product and who your users should be, but... there isn't a recipe. It comes down to think really hard and use your judgement to figure out who you're really building this for.