Why a treaty-era battlecarrier wastes tonnage

How sensible is an Admiral-class battlecarrier carrying about thirty aircraft?

It is a poor compromise; a proper carrier uses the tonnage better and avoids paying for two diluted roles under treaty limits.

An Admiral-class hybrid carrying about thirty aircraft gives up air-group capacity compared with a proper carrier. Heavy guns and carrier machinery also prevent it from becoming an efficient battleship for the same displacement. The treaty system makes that compromise even worse because the ship consumes scarce allowance associated with both roles. A dedicated carrier therefore produces more useful aviation power from the available tonnage.