It's what many top critics on Rotten Tomatoes have said- yes it did do so well and was so successful because of the tech and visuals, at the expense of having a good plot, script and characters. The visuals and technology are indeed what made this film so successful, and without those elements it would not have received even close to the amount of praise and money it got. The praise it DID get were predominantly focused on the tech and visuals. Many of the people who DID praise it even said flat out that the plot and characters were bland or even outright bad. And after getting over that initial wow factor, praise for the movie has died down dramatically and you don't hear people talking about it (or its looked back on as a forgettable story with some nice eye candy). On the other hand, whether you look soon after they were released or decades later, there's still people who are gaga over the likes of the original Star Wars movies, Alien/Aliens, the original two Terminator movies etc). Or in more recent times, Harry Potter (or the film versions of Lord of the Rings, though that plot and characters was already adored for many decades due to the original books).
Hell the main consensus caption on Rotten Tomatoes reads-
It might be
more impressive on a technical level than as a piece of storytelling, but Avatar reaffirms James Cameron's singular gift for imaginative, absorbing filmmaking.
Numerous quotes from top critics, ones from (this first batch will exclude the "rotten" reviews and only focus on positive ones, to further emphasize that even many positive reviewers were far from impressed by anything other than the visuals and tech)-
The narrative would be ho-hum without the spectacle. But what spectacle! Avatar is dizzying, enveloping, vertiginous ... I ran out of adjectives an hour into its 161 minutes.- David Edelstein (New York Magazine)
For all the grandeur and technical virtuosity of the mythical 3-D universe Cameron labored for years to perfect, his characters are one-dimensional, rarely saying anything unexpected. But for much of the movie, that hardly matters.- Claudia Puig (USA Today)
As visionary tour guide, Cameron has no equal. Predictable story, clichéd dialogue and logical lapses aside, he's still the man we want leading us into his Pandora's box.- Roger Moore (Orlando Sentinel)
Along with the eye-popping visuals in writer-director James Cameron's sci-fi epic, there's also a lot of eye-rollingly silly stuff.- Joe Neumaier (New York Daily News)
If only Cameron, who also wrote the script, had spent as much time on the story as he did the effects he uses to tell it.- Bill Goodykoontz (Arizona Republic)
The much-hyped sci-fi actioner Avatar is the perfect showcase for Cameron's strengths...and his flaws.- Keith Uhlich (Time Out New York)
We're not here for the plot, we're here for the cool- CGI/motion capture/movie magic, and for 2 1/2 hours, this movie never disappoints.- Richard Roeper
As visual spectacle, Avatar is indelible, but as a movie it all but evaporates as you watch it.- Owen Gleiberman (Entertainment Weekly)
If your exhilaration with the (approximate) first half is undercut by an increasingly deflating pffffftttt sound, Cameron nonetheless has delivered the screen's most anticipated and persuasive blend of live-action and motion-capture animation to date.- Michael Philips (Chicago Tribute)
A movie whose effects are clearly revolutionary, a spectacle that millions will find adventure in. But it nevertheless feels unsatisfying and somehow lacks the pulse of a truly alive film.- Jake Coyle (Associated Press)
It's rare that even the top critics were praising the plot or characters. Even when they didn't outright criticize those elements, they largely glanced over it in order to rave about how technologically amazing and pretty the movie was. That's not even including the top critics that WERE initially negative and weren't as easily suckered in by the expensive eye candy-