When carrier gunfire does not prove a design need

Does HMS Formidable's gunfire at Cape Matapan justify heavy surface guns on aircraft carriers?

No. Formidable chose to join a favorable action, which is different from depending on heavy guns because escorts and carrier doctrine have failed.

A carrier forced to use its guns against a surface threat has usually suffered a major doctrinal or screening failure. HMS Formidable at Cape Matapan provides an apparent exception because she joined British battleships firing on the Italian fleet. Formidable's gun crews chose to participate in an already favorable action instead of needing the weapons to escape an uncontained attacker. Opportunistic gunfire therefore does not justify designing a carrier around close surface combat.