It seems to me that despite the tech, Netflix video quality is really horrible. Youtube is consistently much higher quality, even though Netflix's own "fast.com" tells me my connection is capable of 75Mbps downstream. Which should be enough for crisp 1080p. Multiple times I've been so frustrated with Netflix's quality that I've started a movie, stopped it because it looked like something out of a VCR, torrented the true 1080p version and watched that.
Most likely you're watching in 720p.
In Chrome, Firefox and Opera you're getting 720p max.
To get 1080p you need to be watching in Internet Explorer, Safari or on a Chromebook.
To get 4k you need to be watching in Edge and have a 7xxx or 8xxx Intel CPU and HDCP 2.2 enabled display.
You can actually get some content in 1080p in Chrome and Firefox with a browser extension. It is somewhat unreliable however and some videos still get capped at 720p.
Chrome extension (with explanation of how it works): https://github.com/truedread/netflix-1080p
Firefox extension (unfortunately doesn't seem to work at the moment): https://github.com/vladikoff/netflix-1080p-firefox