I'm afraid that would mean, Legends quite missed the entire point.
The Republic is the voluntarily formed democracy with a constitution, built on principles of freedom, peace and justice. This was overthrown by Palpatine who declared himself to be an Emperor. The Galactic Empire is actually the Galactic Republic that fell under the control of an illegitimate regime. The rebels fought to restore the Republic, to restore democracy in the galaxy, to force out the illegitimate regime and replace it with the legitimate, constitutional, democratic government.
Disney made some serious missteps, because the "Galactic Concordance" implies that the Alliance to Restore the Republic and the Galactic Empire recognized each other as two legitimate factions, whereas that's something you can never do in this situation, unless you give up the very principles you're fighting for. Those "imperial worlds" were Republic territories under the rule of an illegitimate regime, and the idea that they were meant to be recognized as legitimate independent states, moreover, to recognize the Empire itself to be a legitimate and independent state is to position tyranny and democracy, as well as legitimate government and illegitimate government as two equally valid.
No wonder George Lucas himself described the situation of the "imperial worlds" he wanted for his third trilogy like this: "The stormtroopers would be like Saddam Hussein’s Ba’athist fighters that joined ISIS and kept on fighting. The stormtroopers refuse to give up when the Republic win."