TV show creators understood and planned for people watching their shows in a variety of environments, with varying degrees and kinds of attention. A lot of what made for example X-files and Sopranos compelling was a willingness to break this convention, so it was still firmly in place by the late 90s.
You could also maybe reasonably claim that all TV shows before those were bad as well. But then you need to view netflix as reverting to the norm rather than being a novel travesty. We are simply exiting a 20 year anomaly where TV was good.
I'm not quite making that argument here though. I think there was good TV before the 90s, so I think this is a constraint on the form that good creators can work through and still make compelling art. Why netflix can't is an interesting question but I think this avenue is a dead end for understanding it.