You're trading one filter bubble for another. Unless you want to see how the population of another country experience propaganda, I don't see how it could be useful. You could do critical thinking on any source, not just alternates.
Although with Russia Today, it takes a pretty large effort to filter out the information from between the propaganda. Al Jazeera on the other hand has a fairly high signal-to-noise ratio.
Apart from what the others replied(those networks will show stuff that isn't 'interesting' for some demographic), having the 'your' and 'mine' sides of the story is pretty much necessary to approximate the 'true' side.