That is way overstating your point. The Corvette is still playable. It just doesn' have nearly as much adaptation for setup as the number of upgrades would suggest. The biggest advantage it has is just how much it changes how your opponent plays.
Consider that for 110 points it has 24 HP. That's 1 less than 5 X-wings and it can get an auto-evade, shoot before the X-Wings, deal more damage than the X-wings, and regenerate shields. It's a potent ship, but proper use reuires it to be under 130 points, and with a squad built to use it. You can't load it up with upgrades. You can't expect it to be dealing all the damage, but you can certainly use it to control the field, and controlling the field wins battles. It requires thought to play and build with that far outstrips anything X-Wing has needed before. That doesn't make it bad.
Not really true in the damage department. A Corvette can shoot 4 times a turn (remember that the quad's second attack can only be done if the first misses) for 15 potential damage a turn (if you beef your main weapon with all spare energy, which would leave nothing for defense). A flight of Rookie X-wings tosses 15 dice minimum as well. With the advantage of being able to focus or target lock all their shots.
Also, "you can't load it up with upgrades" sounds a bit counterintuitive for a ship riddled with upgrade slots.
I said Can outdamage the X-Wings. Specifically against low agility targets where the more focused attacks do the most damage. It won't usually, but it can. And that makes it powerful all things considered.
Beyond that, do you fully load a Falcon with upgrades? How about a Firespray?
I certainly don't. Those are options for small precise combos. Not FILL ALL THE THINGS! slots.
The rules with upgrades will always be "as few as possible" for a reason.