I don't think that in itself is a change in viewing habits. There's been plenty of filler tv trash for the last half century, and I've used it in the way you describe even before netflix existed
no it really did.
"Shipping" is a classic trope where 2 characters have a will they won't they relationship for several seasons. It is always a good B story to fill otherwise empty space with when writers run out of material.
The name literally implies what it is, you are "shipping" a script. quality is slightly irreverent
As for original programming seemed dumbed down, I'd argue that for whatever reason (general technical advancements, maybe), it's far easier to make dumb shows, with higher production values. That's how you get wannabe prestige dramas that ape the style of The Sopranos, Mad Men, even costume epics like Game of Shows, but end up being far more vapid and worse in writing or plot. It's sort of how even box office stinkers these days look much better than bad movies used to do.