nothing wrong with taking a solid design and up grading it with current metallurgy, composites, avionics and weapons... the problem comes in as with the A-10 when the tooling was intentionally destroyed might better pay for new tooling
There’s nothing wrong with using proven designs.
While I value a proven design, there are considerations:
Metal fatigue.
Spare parts availability.
Inventory attrition.
Avionics equipment limitations.
Maneuvering envelope limitations.
Changing mission parameters.
You can only upgrade an old design so much. Putting an old design back into production from scratch is very costly, and almost never done; attrition alone is going to ultimately end its career.
(My father was an aircraft designer. I have more than a passing knowledge of military aircraft and their history.)
When something’s at the end of it’s service life,it has to be replaced.But the design was solid.
nothing wrong with taking a solid design and up grading it with current metallurgy, composites, avionics and weapons... the problem comes in as with the A-10 when the tooling was intentionally destroyed might better pay for new tooling