What is your opinion on Russian rock music?

Well, Aria and Kipelov shouldn't be considered part of Russian rock. It's heavy music, and it's better not to lump them together. They actually reach a world-class level. These are two bands from Russia that are definitely known outside of it. This is confirmed by my personal experience. Moreover, the fact that they perform with bands like Rage speaks for itself.
In general, Russian rock is very boring and monotonous; you should only take a few bands into account – Kino (although it's already incredibly tiresome), DDT (these guys are cool), Nautilus (no comment). The rest are not "true." Kukryniksy are so-so – not repulsive, but I definitely wouldn't add them to my playlist.
Regarding KISH and Rammstein, it's quite possible that they were planning a joint project – two stupid bands playing stupid music with meaningless lyrics, pure commerce. They suit each other. In my opinion, KISH is one of the most shameful phenomena for the domestic scene. I'm not even talking about the fact that all subcultures disown them (punks say they're not their guys, rockers say the same). We need more quality bands that play something different than what they always play (in Russia, they only make power and heavy metal), but new, in-demand styles. Maybe then Russian music will stop causing such prejudice.