The fleet-design trade-off between quality and numbers

Can a fleet of more numerous but less capable ships overcome individually superior units?

Yes. Quality must be balanced against numbers, mission fit, and local concentration, because several adequate ships can overwhelm fewer excellent ones.

A deliberately rough quality-versus-quantity model shows why a fleet cannot optimise one ship for a single role. Even an excellent gun cruiser becomes a poor overall solution if it lacks protection against aircraft or cannot perform other required missions. Several merely adequate ships may create favourable local odds against fewer superior units, especially when they can concentrate together. A force's utility depends on mission fit, the enemy's numbers, and the mistakes or unexpected events that disrupt a neat calculation.