Using proof of concepts for critical complex project steps greatly increases probability of project success. Proof of concepts should be intentionally included in the overall project plan and schedule.
Application owners are driven by functional requirements and may not be able to take the time to perform the AAM project.
Application owners are driven to deliver functional capabilities to users and keep the application solution technically viable and as free as possible from technical debt. This causes application modernizations to require a series of projects where technical improvements are performed with functional releases.