Even in 1971, when the partisan divide had much more crossover than it does today, just 25% of journalists identified as Republicans. By 2014, that number was 7% according to the Washington Post (https://www.washingtonpost.com/news/the-fix/wp/2014/05/06/ju...). As the Post's Cillizza points out, that number is for all journalists in the US, and is likely much lower in major media outlets in urban centres that are already often 80%+ Democratic voting in the broader population. With further partisan polarization and the closure of local news outlets, it's likely that percentage is negligible in the major, invariably big-city based outlets used as sources on Wikipedia.
Whatever you think of Biden, the unanimous blackballing of the Hunter Biden laptop story as "Russian propaganda" outside of explicitly right-wing news sources, including banning it being sent over private message on the two largest communication platforms on earth, is a pretty astounding example of how far that's gone. Anyone who wasn't being deliberately obtuse that looked at the New York Post's reporting could see it was likely real. Seeing journalists ignore the story at best and widely cheer on censorship of stories based on their political implications is a massive deviation from the premise of a media generally willing to cover all important stories that Wikipedia is built around.