Marginal advance?
Leaving aside that few people are going to be willing to trade colour information for depth, colour filter anaglyphic 3D used improvised camera rigs with chronic registration problems. These persisted with polarized 3D, because alignment is basically mechanical. Even in the “best” of these films (like 3D House of Wax,) you’ll find scenes where one eye’s image is slightly higher than the other, of even scaled slightly off. Because you had to synchronize two projectors, it was common for images for each eye being slightly off in time, especially if the film had been spliced at any point. This created a significant problem for viewers.
Directors of earlier 3D movies did not understand that rapid shifts in focal depth would create discomfort for the audience, and even if they did, they did not have the means to mitigate this in post production. This was a huge technical problem to overcome, and now it is trivially easy to edit a film with this in mind, where it was practically impossible before.
Earlier iterations of 3D were problematic in that it was not practical to present complicated composite shots, limiting filmmakers to practical effects for their films. Before, if you were looking at it in 3D it’s because it was something they were able to physically place in front of the cameras – now, filmmakers can present a perfect 3D scene that’s made up of hundreds of discrete elements, whether they are photographic elements or CGI.
On the presentation side, almost the entire infrastructure has been replaced with an eye towards 3D, instead of just making do with whatever happens to be there. Screens are engineered to kick light back without breaking its polarization, vastly improving on the murky dimness of earlier 3D.
The main thing, though, is that the industry has now embraced 3D, and so the calibre of films presented in 3D has changed significantly. It used to be that if it was in 3D, you were virtually guaranteed that it was going to be rubbish. Because the technology has advanced to the point that it has an attractive cost/benefits ratio, we now have great-looking 3D spectacles from top-tier filmmakers and “A” list talent.
There is a vast difference between It Came From Outer Space (or even in Friday the 13th Part III) and the current crop, and it’s a bit silly to deny it. It ain’t going anywhere but up.