I don't think what you term 'falsehoods' in fiction per se are harmful (more on that shortly). Falsehoods are most harmful when they're indistinguishable, or hard to distinguish, from the truth - or indeed masquerading as truth. In that sense, social media has the most potential of the things referenced above for damage via insidious falsehoods. Phenomena like self-curation, implied endorsement, groupthink, lack of nuance, social pressure to conform in public (to name a few) all cumulatively add up to an objectively skewed picture of reality, but which most people will accept as being ostensibly real/true. Cf. layers of bias in news media.
I think fiction is net beneficial. We know, upon opening a novel, say, that what's contained in the pages is the product of the author's imagination. The world depicted most likely takes its cues from the world we live in, sure, but we know from the outset that that world is not real. Because we understand that framework from the moment we begin, we are able to compartmentalize and to compare/contrast that world and its characters, on the one hand, to/with our world and the people in it. Critical thinking through analogy leads us to learn more about - and understand more deeply - the world we live in, to consider points of view that are different from our own, and to identify parts of ourselves and our worlds we wish to improve and why. It's hard for me to see how that's harmful.
Female finance lawyer here. My field skews male, especially in the higher echelons/partnership level.
Few people willingly sign up to be on the vanguard, agreed. And while I don't particularly want to be on the vanguard, given that I've been at this a while and been through some things, I may as well use that experience for collective good. I mentor the hell out of younger attorneys. Like you, I've stopped sugarcoating everything. I think there's good to be done in giving other people more complete information than they would have otherwise.