They’ve never been politically neutral.
True, but from about 1865 to 1960, in fact they viewed it as their JOB to appear neutral and to seek neutral writing. See my comment to Lou above.
I helped with a great book by Jim Kuypers, a communications prof at VA Tech called “Partisan Journalism,” and yes, for about 100 years most papers abandoned political slant except for the editorial page. This was due to business reasons-—at the time, they lived off subscriptions (unlike papers from 1830-1865 or unlike media today, which is bankrolled by huge lib corporations and can ignore viewers or readers).
There were exceptions like Walter Duranty, but the beat reporters prided themselves on people NOT being able to tell their party affiliation by their articles.