And this is where I'm confused: where does a dev learn the skill of figuring out how long a feature will take before figuring out the user flows and data struct

And this is where I'm confused: where does a dev learn the skill of figuring out how long a feature will take before figuring out the user flows and data structures. I've never worked on a project where I was estimating something at a scale of 6 months. But if you ask me whether something will take 1 week or 4 weeks, before I've broken the task down, my intuition is going to scream "I don't know the answer to that." If I told you "Somewhere around 1 week to 2.5 months", would you accept that answer? Or would you think I was trolling you and we should have a conversation about my performance and place at the company? If I instead told you "2 weeks", how would that be anything other than a lie?