I just realized something: even without superweapons, any Legends faction worth the name would simply stomp. Why? Because the difference in scale when it comes to naval artillery is like the distance between Heaven and Earth. Canon naval artillery is just plain unimpressive, as seen in Rebels and how in TLJ they needed to bring a specialized planet-bombardment vessel to raze the Resistance base.
Contrast that to Legends starships, with even those built and operating in the 3000s BBY having simply overwhelming naval firepower. For instance, here's Darth Malak's destruction of Taris.
Note that Darth Malak's flagship is by no means a specialized vessel, but just your standard Interdictor Class Cruiser for his breakaway Sith Empire. It should also be noted that a refitted variant of that same class also serves in the mainstream Sith Empire's fleet, with one such ship, the Tears of Taris, flagship of Darth Charnus, actually being a veteran of both the Jedi Civil War and the First Jedi Purge.
In short: even a relatively-outdated cruiser of the Sith Imperial Navy outguns the best ships of canon. How much their top-of-the-line vessels, like the Harrower or the Terminus?