While such definitions are good for casual conversation, they are not good for scientific discussion. Or you end up with nonsense like “my doorknob has consciousness“, well, lets define what consciousness is first.
With “consciousness” in particular having good definition became important since there are a lot of discussions about “is AI conscious?” which might in the future dictate policy decisions.
There's nothing absurd about “you know when you see it”. Those are just things we don't have (or can't have, or don't yet have) good definitions for, but do exist.
"Family resemblance" [1] classes of things are often like that.
"What is a game", is a classical example. Any definition you can give can be violated, including "having a goal", or "not having real impact" etc. And yet we know a game when we see one. And there's lots of other such distinctions.
[1] https://en.wikipedia.org/wiki/Family_resemblance