Democracy is a political tool to keep the plebians in line. As political tools for that purpose, there are far worse, but the fact that actual rational adults believe in all the fluffy fairy-talk when it comes to what democracy is, simply proves how effective the idea of seeming inclusion is when it comes to a method of rule.
Individuals who want power came to realize that it's easier to keep the rabble in line with high-ideals and seeming inclusion, than tight-fisted authoritarianism and hang-em-all attitude.
I'm not arguing for, or against it. I'm of the mind that most people, including me, really don't give two shits what form of government exists when the chips are on the table (as opposed to sitting in the comforts of our modern societies that let us live in ways most of human history wouldn't be able to imagine, as we sip our wine and make high-minded remarks about things on the internet), as long as we get to live our lives below a certain stress level. I do think, of the varied methods of ruling people, democracy has a lot of positives, in that I suspect the stress relief valve on the system is far higher than most other political systems (ie: the point where the people say enough is enough and go about overthrowing things). The major downside is that the illusion of inclusion makes for a poor government when something requires a quick response.
Also, while I love Legends of Galactic Heroes, it still managed to retain a bit of naive idealism, despite everything it did to shed a cynical light on the interweaving of politics and society. Nothing particularly wrong with that, but I've often wondered what kind of show it'd have been if it had gone all in on laying out how things (can) work.
Lastly, I don't think the purpose of this show is to judge democracy. The rats are obviously an allegory for humanity (an Animal Farm for our times?
), for the purpose of the viewer, so it makes plenty of sense that they'd bring democracy into it. I thought it incredibly amusing (and ironic) when Saki made her remarks about how they shouldn't judge the rats by human ethics/morality.
I don't really buy into the idea of species-level self-flagellation, myself, so if the intent of the show (or anything else) is to make me sit in self-reflection and /wrist over the state of humanity, I chuckle and enjoy the story, and move on.
I see the story ending in one of two ways (if I'm wrong, please don't tell me via pm):
1) Going all in and ending with the rats as the dominant life form on the planet. As Saki is narrating this story, from what is presumably the "future", this seems unlikely, though if the author had a personality like mine, this entire story would be the result of Saki as a slave to the rat kingdom, in a state of near-catatonic shock, thinking back to her happier times.
2) Taking a more idealistic approach of a more balance partnership between humans, rats, and human's approach to their "power", resulting in a new world that probably doesn't answer any of the zillions of questions of how it would work, but at least ends on an upper, rather than a downer.
I'd prefer #1. However, no matter how tragic a story, it usually doesn't earn all sorts of awards and gain mass appeal, like this one apparently has done, if it ends in such a depressing way, so I'm guessing some sort of bloody immediate future is going to result in both the humans and rats to self-reflect and realize the status quo can not work any longer (putting aside whether it can or not from the viewer's perspective).