Flat hierarchy often communicates structure with less chrome. The useful question is not whether the idea sounds persuasive. It is whether it helps someone understand the work, make a decision, or complete a task with less friction.
What is happening
Cards are useful interaction boundaries, but they become visual filler when every sentence receives a box. Nested cards make the hierarchy especially hard to read.
This tends to become visible at the boundary between the organization and the person encountering it for the first time. Internal familiarity hides effort that remains obvious to a customer, reader, applicant, or collaborator.
A practical response
Use sections, columns, rules, and spacing first. Reserve a card for a distinct object that can be selected, moved, or acted upon.
The aim is a smaller, clearer system: one source for the record, one visible hierarchy, and one next action that behaves as expected. That approach improves the immediate page and makes later application or database work easier to add without rebuilding the public surface.