That's the difference between "inventing things" and "discovering things".

If you believe you're inventing a solution, doing just enough to solve the immediate problem and stopping is the consequence.

If you believe you're discovering a solution, diving deeper into the problem to try and uncover some truth about it, stopping at the first solution is not enough if you can't explain why it works or why it will keep working in the foreseeable future – because that involves solving a category of problems, not just this single instance.

People like to think in terms of under vs. over engineering, but I don't think this is the right angle to discuss. You can certainly over engineer the first solution because you focused on a single instance of a problem and "missed the forest for the trees" – identifying a general pattern is useful to find what category of problem you're dealing with, research prior-art on it and uncover elegant/economical solutions.