The article says “Across a spectrum of major policy issues, majorities say that each party’s positions are generally mainstream…”
That’s crap. As I tweeted, four of the six Republican ratings for extremism are higher than any Democratic rating. The GOP is much more extreme than the Republican Party. The media likes to give a lot of attention to AOC but New York elected an ex-cop as the mayor. Biden was possibly the most moderate candidate in the 2016 Democratic field.
The two parties are not the same but the media is afraid of being seen as having a liberal bias so they do things like this.
Here’s a second one that carries over the misleading impression of the first one.