History in particular is rapidly approaching post-truth as a knowledge domain anyway.
There's no short-term incentive to ever be right about it (and it's easy to convince yourself of both short-term and long-term incentives, both self-interested and altruistic, to actively lie about it). Like, given the training corpus, could I do a better job? Not sure.
"Post truth". History is a funny topic. It is both critical and irrelevant. Do we really need to know how the founder felt about gun rights? Abortion? Both of these topics were radically different in their day.
All of us need to learn the basics about how to read history and historians critically and to know our the limitations which as you stated probably a tall task.
What are you talking about? In what sense is history done by professional historians degrading in recent times? And what short/long term incentives are you talking about? They are the same as any social science.
"History done by professional historians" comprises an ever-shrinking fraction of the total available text.
Gen-pop is actually incentivized to distill and repeat the opinions of technical practitioners. Completing tasks in the short term depends on it! Not true of history! Or climate science, for that matter.