As someone who's a similar age, I wonder if that's a bit of rose colored nolstagia? Sure, these days the JS ecosystem is incredibly fragmented.
Back then it was CSS that was so rapidly evolving nobody could keep up. Remember the ACID tests? And that was even before flexboxes made things both simpler and more complicated.
Then there was the streaming wars, where RealPlayer and Flash and ActiveX and whoever else competed to be able to deliver <video>.
And what we solve now with CSS layouts and React components used to require frames and iframes and sprinkled JS drop downs that spoke to ColdFusion templates served from a single old Apache instance shared between a thousand users and constantly crashed, and https cost like a thousand dollars and couldn't be used internationally...
The web was never simple. We were just younger then and our neurons weren't so degraded yet. /sigh