Mutation is random or at least not specifically directed toward a goal. Selection determines which changes survive. Selection is occasionally random, as in mass extinctions, but generally it fine tunes things.
The important concept here is that there is no direction to change. Things do not change towards a goal. Selection may look like a goal, and some writers loosely speak of selective pressure, but selection prunes. It does not direct.
If mutations were biased toward adaptive change you would expect extinction to be rare. But most species fail to adapt to sudden large changes, and extinction is the rule rather than the exception. The large plants and animals that survive mass extinction events and najor climate changes tend to be the smaller and less specialized ones.
There was a recent thread on the ivory-billed woodpecker. It has a near cousin, the piliated, that is slightly smaller and a lot less specialized, and which has never been threatened with extinction.
We've been here before. Please...a single example of a positive mutation