It’s a doctrinal thing again. As long as she only goes up against 6” cruisers or destroyers (or merchant raiders) her 8” will allow her to set the range of the engagement. The squadrons embarked will allow her to dominate the South China Sea, say, outside of a War against a hostile Pacific Great Power.
She’d have been incredibly useful at the Falklands or Coronel, for example. Transported to WWII she’d have been excellent as a raider hunter in the Indian Ocean.
As long as she stays away from anything carrying more than 8” guns, that is.
With 26 aircraft, a Pegasus could probably do a decent job against a heavy cruiser as long as she can stay out of gun range. I doubt the bombs and torpedoes available at this point can deal with an actual capital ship (at least not with only 26 aircraft) but they can probably sink or cripple an 8" cruiser. At worst, they could set the conditions for the Pegasus to finish off her adversary with gunfire.