Instruct the wise and they will be wiser still. Proverbs 9:9a
Some surfaces are difficult to paint on. The paint doesn't want to stick, or so it seems. Better, the paint isn't being absorbed by the surface. Try to paint on glass versus wood. Glass won't absorb paint, but wood will.
The "surface" of our heart, or attitude, either absorbs wisdom, or it won't, to varying degrees. You can have the wisest man on earth as an instructor, but some people have a sealed surface -- nothing soaks in. I think pride is often the sealant. Recall the Jewish leaders in Jesus' day, hearing but not understanding. They were sealed against believing Jesus. His parable of the soils is similar in that it stresses the condition of the heart.
This verse implies that humility is a prerequisite to becoming wiser. It is the opposite of pride, and connotes an openness, a teachableness. A wise person is also at least somewhat humble, hence he can gain more wisdom. Of course, one can be open to anything and everything -- too open, and absorbs untruth. But I think that is what being called "simple" in Proverbs alludes to. The cure is discretion, which starts with one's willingness to revere God.
Would that we all would have open, absorbent surfaces toward wisdom.