To say it's biased to the left requires some agreement on what scale to use and where neutral is. I don't think there is such an agreement. One niggle with you

To say it's biased to the left requires some agreement on what scale to use and where neutral is. I don't think there is such an agreement. One niggle with your linked article is it says it's biased because it goes on about Trump's impeachments and doesn't say similar stuff about Obama but you could argue that's maybe because Trump got impeached twice and Obama didn't, rather than Wikipedia's biases or lack thereof.