I don't think it's a problem that needs fixing. I think of it like this - Twitter labels accounts that are Russian government accounts so that the public is aware of where the information they are seeing is coming from. That same benefit in the context of misinformation / selective publishing would go to the public if it was known that companies lean a certain way. For example the public knows that Fox leans right and MSNBC leans left.
The media doesn't "lean left or right" for the most part. The media acts as a magnifying glass to foment public opinion. The father of modern journalism Walter Lippmann penned a book about this very thing literally 100 years ago (also it's in the public domain now, it's a great read!) https://en.wikipedia.org/wiki/Public_Opinion_(book)
To even imply MSNBC is "left leaning" is absolutely hilarious however. Though I suppose people so easily forget their Nazi comparison of Bernie Sanders
