Pareto is not a solution to solve the case but a way to focus on the key topics in order to be faster.
It can be applied to many situations weather it’s quantitative (eg. market sizing, revenue estimate, cost estimate) or qualitative (eg. brainstorming on root causes of a certain issue.
This is particularly useful when scope of engagement / case is unclear or too wide, and will help you justify why to focus on the priority topics that has the most impact on the issue.
hope this helps