They're trying to restore a Republic (that confusingly has a princess and an order of quasi-religious knights, which sounds more feudal) that has "decayed" into an empire.

Nobody is doing that until Episodes IV-VI. In Andor's time it's simply a rebellion to end the empire. It's the opportunists who who turn it into restoration of the republic and no radicals survive to oppose them.

If Nemik were alive when the Rebellion army was training and fully professionalising on Endor he would have insisted on theoretical education forming part of the the Rebellion army's curriculum and there you go, you have a real revolution instead of a restoration.

The problem is that anyone who would've opposed a restoration and insisted on something different is dead, or they're like Saw who was intentionally kept on the fringe by these liberals because they knew he was a threat to them. They call him "mad" not because he's actually mad but because he does not want what they want, and Saw openly discusses the different views everyone has with Luthen when trying to pry into what Luthen's real ideology was. Luthen, like Lenin, had one true ideology, the ideology of revolution, and everything else was subordinate to achieving that one task first and then transitioning to the task of actually taking power when it was clear the first revolution alone was not going to achieve socialism. This is exactly the mindset we see in Luthen, except one problem, he and everyone else dies in this universe because it MUST fail because Disney's sequels are ideologically dogshit. And that's why they suck ass and feel bad to the audience too.