[CaptainCrunch]

When you look at the various source books and the essential guides including the Essential guide to Warfare. The Star Destroyer was designed with specific tasks in mind, and because of that overall it was not a really good design as the Rebellion gained in strength.

During the Clone Wars the main Republic Star Ships were the Venator and the Acclaimer. These were ships designed to fight a war.

The Venator was meant to fight battles as a Carrier and Assault vessels. It carried hundreds of Star Fighters including the heavy ARC-170, the Z-95 Headhunter and the V-Wing fighters. It had 8 heavy Turbo Lasers for ship to ship battles, plus hundreds of light anti-starfighter turrets. They could carry 2000 clone troopers and their equipment including walkers. The Venator could also land and act as an assault base.

Basically in a battle, the Venator would launch an overwhelming wave of fighters to overwhelm the enemy and standoff with its heavy Turbo lasers.

The Venator worked in conjunction with the Acclaimer which is like a modern troop carrier that could double as a carrier. But could carry 16,000 clone troopers and their equipment it was designed around orbital bombardment but could reconfigure to ship to ship using a barrage of missiles, and had a ton of light point defense canons. Again the Acclaimer was designed to fight in a war.

The Empire decided after the war that the need for those type of ships wasn't needed. They weren't going to be facing an organized military opposition. More along the lines of pirates, smugglers, and light capital ships run by small insurgencies.

So they designed the Star Destroyer to be intimidating work effectively as blockade ships, and intimidate planets with orbital bombarment. For that they were probably well designed. But the Star Destroyer lacked point defense. They carried very few fighters that weren't hyperspace capable and were unshielded, they also didn't expect to face ships that could stand toe to toe with them with their heavy quad turbo lasers.

So when the Rebellion got organized and stole the Calamari Cruisers and the X-Wing hyperspace capable shielded fighters the Star Destroyers while still awesome in a stand up fight, didn't function really well against the hit and fade of the Rebels hyperspace capable fighters or a determined fighter attack. Their heavy turbolasers weren't super accurate against a nimble fast ship, and the Star Destroyer didn't have point defense turrets or super accurate rapid firing light turbo lasers.

Also unlike the Venator and Acclaimer who had protected shield generators. The Star Destroyers were designed with the Shield generators, scanners, and communication array in an exposed position, because they didn't expect to be seriously challenged by dozens of fighters at a time and capital ships wouldn't last long against the Star Destroyers sunday punch.

We saw in Rogue One that problem was really exposed when the Rebel Bombers did a heavy Ion Torpedo run against a Star Destroyer.

But we also saw the height of Star Destroyer power and effectiveness in Rebels when Star Destroyers with Interdictors basically trapped the Rebels and unleashed a hellish orbital bombardment.