RT is not only owned by a foreign state but is specifically owned by a state which attempted to deceptively influence Google's home country's elections, partially with the help of RT. RT is undoubtedly Russian propaganda and can't be anything else; anyone at RT who genuinely wants to provide a view that isn't uniformly pro-Russian risks retaliation from the government.
If the scenarios were flipped and Voice of America were peddling propaganda to influence Russia's next election (which they probably actually are doing), Yandex would have a pretty valid reason to lower the rankings of Voice of America stories.
I'm not sure the impact so much matters as the intent. Even if it wasn't really a big threat, and even if Trump would've won without any sort of interference (which probably is the case, but it is and will be impossible to truly know), the fact that they did it at all shows they're trying to game the system, partly by gaming Google. Google is now going to make it harder to game.
It is a bad precedent to de-rank results in this way, but I think this is a special circumstance. I agree that a better approach would be to provide warnings and context rather than merely trying to push things down.
I think some of the election-related stuff is mostly politicization. If you follow some of the hearings on the subject of Russian propaganda (cspan has some) it seemed more that they were targeting and prodding cultural divisions.
Organizing anti-immigration rallies at the same time and location as Muslim rallies and pushing racial and cultural divides. It seems like their focus is to polarize people and try to promote extremism.
But I don't believe that Vice has quite the divisive and disruptive agenda that these state sponsored propaganda bullhorns have.