I'm not sure that gaslighting means what you think it means. In any case, the rightwing doesn't have anywhere near the reach and audience of the unambiguously left-leaning mainstream media. Fox News, for example, doesn't have even remotely the reach and impact of any member of the mainstream media. Fox News wishes they were in the mainstream media, but they're barely a drop in the bucket. They don't do their own original reporting, save rare exceptions, and they cannot mold the opinions and attitudes of the masses the way the MSM can.The rightwing has waged a proverbial war on the media for years, gaslighting them to the general public.
So it stands to reason that public opinion of the media might be affected by that, if for no other reason (and there are surely others)
Journalism is at its core a left of center, liberal endeavor. It always has been and likely always will. That's the nature of journalists and journalism. The mainstream journalists ceased putting their own bias in check, and for the last few years have stopped even pretending. And still today they continue to perpetuate verifiably and objectively false narratives and hoaxes as if they're true. That's gaslighting.
It's not a contest, but it's way worse today than in that 2-year-old piece linked.But guess whose approval and trust ratings are even lower: