You can disable autoplay of previews, and you can disable autoplay of the next episode in a series.
What I would like to see is, semantic search where I could elaborate the shows/movies I'd like to search for: "A classic movie starring Tom Cruise and directed by Steven Spielberg" and Netflix shows me "War of the Worlds" in search results.
I don't feel like Netflix lacks things to watch, I just feel it does a terrible job keeping its suggestions fresh.
Thumbs-down on a video seems to remove the whole category.
You just can't start a service with recommendations as part of your sell... and then bastardize those recommendations into advertisements or original content-pushers. Paying customers eventually lose patience.
If you turn auto play off, there's no way to play anything. You have to just start watching.