Russia and China are both enormous countries formed out of myriad cultures, each of them has dozens of local languages across varied territories, where the thing that connects these territories is simply the fact that they were conquered at some point. Both Russia and China are the results of centuries of kingdoms conquering each other, and both continue to push to expand their borders over ever more areas full of people who don't want to be part of them. Taiwan, Tibet, Ukraine, Georgia... how many territories of people have been claimed as part of these two countries just in our lifetimes. Seriously, how many times does Georgia have to reject being under Russian rule? Russia and China have Russian and Chinese people, sure, that's just a descriptive. By no means does that mean they don't have millions (hundreds of millions?) of people of longer established and more vanishing cultures than the Palestinians subject to their rule without any say in it.
Like, holy crap, the suggestion that Russia or China are the product of self-determination by a united people is insane.