Why a world of Bearn copies sidelines naval aviation

What happens if every Second World War aircraft carrier becomes a copy of Bearn?

Carrier aviation never becomes dominant, because Bearn's speed and aircraft-handling limits would cripple sustained fleet operations.

The counterfactual turns every wartime carrier into Béarn and converts each newly commissioned replacement into the same design. Carrier aviation would struggle to become the dominant naval weapon under those conditions. Béarn's clamshell lift covers offered protection against water entering the hangar, but operating them obstructed the flight deck. The arrangement also meant storing the lift down, whereas a normally raised lift allowed the ship's weight distribution to be considered with that weight already higher. A useful local solution to water ingress thus imposed difficulties on aircraft handling and the ship as a whole.