Requirement analysis is supposed to be done by of the Dynamics 365 solution. The expert could be external advisors/partners or internal team members and should bring in the much needed experience with solution guiding options.
Customers must push their advisors/partners/consultants to seek solution options, both in the form of workarounds and in the form of customizations or extensions when a requirement can't be met with out-of-the-box capabilities. Even when requirements are envisioned to be met out of the box, their mapping must be documented and should be validated during the learning/prototyping phase in the CRP approach.
When a requirement can't be achieved with out-of-the-box capabilities in a Dynamics 365 solution, then the solution analysis stage starts. Poor analysis will add more time, effort, and cost to the project. Every time you get a requirement that needs customization, try to think how the other Dynamics 365 customers are using it. Ask why Microsoft...