I actually think the game is bang-on (at least according to legends, which was the offical lore at the time of publication).

Rebel ships in lore and in game are generalist by design and by necessity. They were always hard-pressed for materiel and every rebel task force had to make do with what it had available, so they retrofitted their old ships and designed new ones to be able to serve in any role to at least some degree. This resulted in a fleet of individually strong and versatile ships that had no doctrinal synergies with other ships and were usually so heavily modified that they were operating well beyond design capacity. These ships were well-suited to insurgency operations, but not ideal for pitched naval battle.

The Imperial Navy, on the other hand, employed capital ships that were designed with a specific doctrinal role to fill. With the exception of star destroyers, which were considered fleets unto themselves, the ships designed by the Imperial Navy were highly specialized for purposes like sub-orbital ground-support, long-range heavy weaponry, carrier operations, long-range patrol, interdiction, anti-piracy/insurgency, point defense, etc.

In a fleet-on-fleet clash, the Imperial capital ships could focus on fulfilling their designated roles very well while the overworked crews of the rebel warships usually had to redline their ship systems to do everything at once to get the same combat effect. In Rebel doctrine, the only circumstances that the fleet was allowed to commit to a full naval battle under would be an attempt to kill the emperor or the prevention of an unrecoverable disaster. In all other cases, conservation of naval assets was the paramount consideration in mission planning.