To be fair, those subs are explicitly political support groups, the fact that they are peddling propaganda or politically aligned news is hardly surprising.
I'm not in complete agreement with you on the MSM question, although I am not American so it may be hard to compare, but in my country Russian propaganda has mainly targeted very specific speaking points (meaning they are simply more present on these than MSM could afford to be before people would start asking "why are our main news channels talking so much about this thing?" and lose interest), with much more emotionally charged language and content than MSM has, and is re-vehicled internally by political groups and activists which are supported by Russia or simply feel a proximity to it (the Far Right and the Far Left generally), and whose militants are usually skeptical of MSM due to their ideological leanings. In this sense, they have demultiplied influence when it comes to a specific public, in comparison to MSM, a bit like Alex Jones in the US I guess, and generally growing distrust in MSM means growing impact for such influence campaigns.
They also have a demultiplied impact due to the nature of the Internet, where it is much easier to expose people to new channels etc. at little cost: I hardly know anyone who actually seeks out stuff like RT clips, for example, but they are much more likely to go viral on my country's Facebook than MSM clips are, because they usually know how to package them and pull the emotional strings which lead to huge shares on social media, while also giving themselves an initial boost by using bots.