Would a simpler FREMM or Legend frigate make more sense?

Would the Navy have been better served by a largely unmodified FREMM or a strengthened Legend-class frigate?

Possibly, but only within a layered fleet that actually fields enough large combatants above the Burkes to protect a lower-end escort.

A simpler frigate depends on the larger combatants that accompany it. One proposed explanation for the new design is that the Navy expects to acquire a larger surface combatant as well. Burkes would occupy the middle of that force, with larger ships above them and smaller escorts providing numbers below. If the larger ships fail to appear, the lighter escorts lose the protection on which that arrangement depends.