In the early days of lazy 24/7 news reporting, you just grabbed a spokesperson from both sides and gave them air time. Voila --- fairness.
But you can't presume both sides are making an equally good case unless you research their claims, a job that reporters are paid to do on behalf of the average less-informed viewer. If you have a partisan agenda --- and I'm assuming every journalist casts a vote -- you have to be ready to report some inconvenient truths. But....if you uncover some shoddy intel on Russian collusion or a legitimate theory of a Covid lab leak, does that wipe out the larger stories about Russian electoral influence and pandemic response? It shouldn't, but of course it does. There are even people on this board who think Donald Trump was exonerated by the Mueller Report, even when Mueller went to the trouble of literally declaring the opposite.
Kinda makes me think of the steroid era in baseball. The drug-free players watched the roid heads elevating their stats and salary, apparently facing no consequences from the league. Until some said f#&% it: if we're not playing fair, and I'm getting no love for playing clean, I'll take the short cut, too. Fox was tv news on steroids, and CNN and MSNBC realized they better juice, too.