Ask HN: How to find out "why does this not exist yet"?

TL;DR: Have an idea of a product. Did some research, building it as simple as glueing together a few open source SDKs with some fine-tuning, plus some devops work, should be quick. It appears to be very valuable, and sexy too.

So i understand it smells bad: i can't be the only person who thought of this, and if it doesn't exist yet, it must be a terribly bad "tarpit" idea that's certainly not worthy of working on.

How to find out why in particular is it unworkable? Any repeatable approaches to do research like that?