The junior developer sees a pattern and thinks why not make this a bit more generic so it handles similar cases. Oh but these cases fit a larger pattern.. and eventually you'll have written yourself an entire framework. This is very valuable, for the experience. Not for the framework, which will never be used. But you should go through it.

The mid-career developer knows this from experience and sticks to the minimum necessary to meet the requirements. Fast and efficient in the short term.

The senior developer mostly agrees with that but also knows that there is nothing new under the sun and all software ideas repeat. So from experience they can selectively pick the additional implementation work to be done ahead of time because it'll save a lot later even if it's not needed yet.

As an aside, this is one of the many reasons why I interview based on discussing past projects and don't care for algorithm puzzles. Unless I specifically need an entry-level developer, I'd prefer to have the person who has written a few silly (in hindsight) complex frameworks and has painted themselves into a corner a few times with overly simplistic initial implementations. That's the person I know I can leave alone and they'll make sane decisions without any supervision. The algorithm puzzle jockey, not so much.