IPTV
A see in the comments multiple people talking about how "cable" companies who have migrated to IPTV has solved this problem.
I'd disagree.
I'm on IPTV and any major sporting event (World Series, Super Bowl, etc) is horrible buffering when I try to watch on my 4K IPTV (streaming) channel. I always have to downgrade to the HD channel and I still occasionally experience buffering.
So Netflix isn't alone in this matter.