I've got a 4K TV and it's placed in a location that I can tell whether or not something is 4K if I sit a bit closer, but the core problem is that it's still very difficult to provide it
true 4K content, since I've not been willing to drop the money for 4K blurays.
I've got a variety of content that is, technically, a video stream that decodes into a framebuffer that is a "4K" framebuffer according to the metadata on the video, but without enough bits for it to truly be "4K"; the same number of bits dedicated to a 1080P video would look just as good.
For all the bragging about how streaming is the future, it seems to me that the companies providing those streams at scale still have a lot of incentive to cut the bitrate back so far that it's not practically a 4K stream anymore, because 95%+ of their audience can't really tell.