A scenario is typically just one narrow manifestation of a much broader problem. Scenario solving is taking one narrow segment of a problem and solving it without considering the scope or context of the problem itself.
Problem solving is considering the entire scope of the problem and implementing a solution. A problem can be thought of as an aggregate of scenarios, the solution to which resolves the majority of the problem's scenarios. A scenario is typically just one manifestation of a much more general problem.
Scenario solving results in a fragmented user experience. While problem solving results in useful primitives that can be composed to build features significantly faster and more efficiently.