I'd argue that such hasn't suddenly become unreliable. It was always unreliable, it's now far easier to fact check (and frequently do so in exchange with experts in a given field, as happens so often here). Now you have a million eyeballs on the bogus claims / data, and those eyeballs frequently have fast, easy access to vast research sources.

Today if the President says something bogus, it'll be fact checked in minutes by a thousand people and that fact checking will be syndicated globally nearly instantly on a dozen large media platforms. By comparison, consider the process, access and distribution that existed at the time of FDR (the things you can get away with when it takes a week or a month for distribution to occur).

We have a lot of historical examples from the last two centuries, to show that data accuracy and reporting in terms of commerce, politics, military, journalism etc. were not particularly extraordinary in the past. Agenda, laziness, bad research, bad reporting, misinterpretation, etc. are nothing new.