I agree with your general perspective. I'd guess that the further back in time you go, the stronger filter bubbles were. One hundred thousand years ago when we all lived in tribes and clans was arguably peak filter bubble. These relatively small groups had their own histories, languages, religions, traditions, etc., and often lived in isolation from everyone else. The diversity was probably staggering. Impossible to imagine. Just look at how alien and unique a place like Japan can get after a bit of isolation.
Today we're quite homogenous by comparison. People on both sides of the aisle believe more-or-less the same things, but we zoom in on the tiny differences and exaggerate them. The media does its best to facilitate this, because its business model depends on eyeballs, and eyeballs are driven by novelty and controversy.