Agreed, and sadly not limited to the US. One of the things I (eventually) realised is that here in the UK The Guardian is equivalent to The Daily Mail, but for liberal intelligentsia instead of Conservatives and UKIP supporters.
I think the idea stems from the way the Graun has opened up it's 'Comment is Free' section which has lead to quite a few low quality opinion pieces particularly 'SJW' esq ones.
The actual reporting from the Gruan is still good quality in my opinion, certainly head and shoulders above the DMs. And whilst the Graun has its left bias it, quite rightly, hasn't been kind to the current Labour party.