The Guardian has always been a newspaper with politics most closely aligned with the Lib Dems. In the past, this meant that they were left of Labour. Labour has shifted waaay to the left[1][2], past the Lib Dems and past the Guardian, so the Guardian no longer finds themselves in political alignment with Labour. I don't think the Guardian have changed their political stance substantially.
It's an interesting observation, particularly for the fact that according to those charts UK's left party has been for the past decades a right-wing party, both on the economics and the liberal/authoritarian axes.
However, I'm not British and I've never followed the politics of any British party, nor my political views have changed substantially in the past few years, so I don't think my perception of the turn to the right of the Guardian in international politics might have been influenced by the shift in Labour's position.
However, I'm not British and I've never followed the politics of any British party, nor my political views have changed substantially in the past few years, so I don't think my perception of the turn to the right of the Guardian in international politics might have been influenced by the shift in Labour's position.