Different mediums.
Game of Thrones absolutely set the bar for the quality of entertainment, both in world building, story development, and effects, that you can expect on your giant 4k home theater. Peter Jackson's films were theatrical releases.
On this subject, I was extremely disappointed with Amazon's "Wheel of Time" which is supposed to be a 7-8 season flagship program for their streaming network. Crappy sets, crappy costumes, ugly actors.
As far as wolrdbuilding goes, I really enjoyed HBO's "Raised by Wolves" and am looking forward to Season 2 of the Ridley Scott produced sci-fi show.
I don’t think that being targeted for different mediums is all that relevant. For one thing, the new Dune is also being released theatrically. The “unfilmable” designation, I believe, has to do with credible execution of fantastic elements (in terms of special effects) as well as the scope and complexity of the overall storyline. Regarding the latter, the Middle Earth and Narnia films actually had more of a challenge, given the overall running time of feature films vs. a season or more of a TV/streamed series.