Biased reporting has always existed - again, no one is claiming utopia without bias. The idea is to have enough trustworthy sources for different points of view, arguing in good faith, for certain positions.
Now biased reporting comes from a few sources - the polarization is evidence of this.
The funny thing is that newspapers often started that way in the US. The reason you would often see the <Town/City Name> Democratic/Republician Gazzette newspapers? Because the ones who could afford to publish small town news were political parties. They did wear their motives explicitly and the eras were hella corrupt but it has precedent.
But my example was precisely about lack of differing opinions. The issue there was consensus in media, that made it look like there is clear agreement of experts about something where it was not the case.
There are periods of more objectivity and less objectivity - not all times in the past were objective, and some were more so. No one has claimed above - a most convenient strawman.