I am sad to Ebert go, his reviews defined the industry, but towards the end of his career he became increasingly hostile toward anything that wasn't "classic" cinema as defined by films which he reviewed during the peak of his career.
By his definition, films were art. New narrative vehicles such as 3D, VR, and even video games were not films and therefor not art.
In this guest post by Walter Murch, he complains that 3D films force the brain to converge focus at objects at unnatural depth of fields - this inability to switch depth of field quickly prevents 3D films from working. It's an uncrossable technological chasm.
I would counter that this argument is flawed on two critical elements.
First, the first film to make use of shifting depth of field was famously Citizen Kane in 1941 - before this, the ability to rack focus just wasn't a thing. Yet films 'worked' before Citizen Kane. To posit that films need this ability to 'work' is to discredit the first 40 odd years of film.
The second is the argument rests on our inability to solve this technological problem - a dangerous and often repeated statement in the history of film. Just as other old men were critical of the viability of sound or color given the enormous challenges the first versions of these technologies had, Ebert/Murch here were critical of 3D at the time when companies like Magic Leap and Lytro were just showing the first signs of promise in crossing this chasm.
"3D doesn't work and never will" is an interesting predication along the lines of "locomotives traveling twice as fast as stagecoaches are palpably absurd".