> I think if we're starting with an individual with no obvious weaknesses, perhaps they are just average at many things for example

I didn't mean that the weaknesses have to be obvious. I agree the first example I used was a blatant one, but in the other case the person had lived 5 decades without recognizing the impact that lack of communication skills had on his life. He always just thought "that's how I am."

So in your case, of someone who is "just average at many things" - perhaps there's a fear of chasing a direction, a reluctance to commit, an inability to focus, etc. that probably got them to "just be ok" and living below their potential, and probably overcoming that thing is a meta-skill that they need to gain.