yes, the Republic was overly bureaucratic, corrupt, and didn't maintain law & order effectively enough. there were valid reasons for the rise of Empire, and although they're unequivocally portrayed as villains in the OT, there are much better ways of developing moral ambiguity than all-out subversion and chaos.
they win, but only after numerous shoahs, the ruination of significant worlds, and a galaxy-wide marathon of torture porn; all because the New Republic was unprepared for the invasion. if the Empire had won, their militarized society would've been far more effective at holding off the Vong, especially with a working Death Star or two, which would've been ideal for taking out worldships.
this means that the galaxy would've been better off under an Imperial victory, which negates the achievements of the Rebels and Luke. there's no point to them winning if it only makes matters worse all around. the OT is about good overcoming evil, and the underdogs defeating a larger, hubristic enemy. while you can introduce complexities to this, it should not be subverted, especially not with nukes made of rape.
and as I said, the Vong have other problems. they rely on biotech, yet they're immune to the Force, in spite of the fundamental link between the Force and all forms of life. it just doesn't work.
I reiterate, the Vong make it so that the OT had a bad ending, and Sheev stood for the greater good. I simply can't accept it, no more than I can accept the Empire being magically resurrected as the First Order, Luke becoming a bitter hermit, massive logic breaks, and Sheev ultimately winning by extinguishing the Skywalker/Solo lines, and working through his OP daughter who also usurps the Skywalker lineage, until Sheev eventually reincarnates and takes over the galaxy again. some things are too much.