Why Invincible worked as a cruiser but not a line battleship

Was the Invincible-class battlecruiser design worth trying?

Yes as a cruiser, but not when used in the line of battle against battleships for which it was never designed.

The Invincible-class concept was worth trying when judged as a cruiser. Its speed and heavy armament suited the cruising functions for which it was developed. The design became vulnerable when commanders emphasized the word battle and used the ships as if they were armored to trade blows with battleships. Its intended role needs to be separated from the later doctrine that exposed its weaknesses.