Avatar Is one of the weirdest movie properties ever. It has a theme park at Disney. Both movies have been nominated for best picture. The first is the No. 1 box office all time. The second is the No. 3. Only Avengers Endgame is above the second one. In terms of gross ticket sales the two films are above all other Marvel movies, Star Wars movies, Lord of the Rings movies, Titanic, Harry Potter, Disney, Fast and the Furious, etc.
And also basically no one cares about it.
If you emerged from a time capsule and read the first paragraph, you would probably think it was one of the biggest cultural phenomena of all time. But beyond being known as the "they're really expensive/pretty" movies, there's been basically no major cultural impact. Almost every actor in the Avatar movies are more famous for a different role. No one quotes it or references it. Most people don't particularly care about Jake Sully or any other character. The soundtrack is good, but most wouldn't immediately recognize it in the same way they would most of the other properties listed above. Other than jokes about how bad the name "unobtainium" is, there's not even any notable memes that come out if it. If you talk to anyone about it you typically get, "Yeah I liked it. Really neat technology." and then the conversation just ends.
I don't know how to better describe it, but it feels like there's this huge vacuum of nothing where the Avatar cultural impact should be.