TBH, IMO this is all a non sequitur

My point is that the nature of digital technologies is such that information is far more ephemeral and closed off than it's ever been, not just for historians but for we, the people who are creating that information. We produce a lot more information, but control and long-term preservation is infinitely harder.

Your observations regarding the challenge of historians is absolutely true. But the effects of technology are entirely orthogonal to that problem.

After all, even if we had perfect digital preservation, what you say is still true, if only because subjugated groups are less represented in the digital discourse for many reasons, including socioeconomics, direct censorship/interference from power groups, etc.