Bad "good ideas"

Hey there! Would like to talk about bad ideas. Not the ones which you reject right away but "nice now, bad over time".

Let me describe the feeling.
-- Such ideas come out as a solution for some problem you notice relatively easily. Might be your personal. And you might've had no affiliation with that market before.
-- Then you start to think of common solutions and can't remember a standard one. Problem seems really obvious to exist and surprisingly there is no popular solution. Boom! This must be the vast opportunity.
-- You start to validate further or build something, show/tell people. They say "Nice", but not really eager to try.
-- At some point you also discover a lot of similar projects which didn't take off and couple of good solutions you've never heard about before.
-- Sometimes you can describe solution as "yet another ..."

Do you see what I mean? Ideas which are so obviously good initially but kind of "bad" after you start to elaborate them. And you can't really tell what's bad about them, they just don't work.
Do you know such bad "good ideas" (problems) yourself? Please, share below.

The main part: I want to understand what these ideas have in common. Maybe there is some cognitive trap which makes them so tempting yet non-feasible really because of fundamental restriction.

*I will share my personal example in comments (which I work on as a product now :).