While wide shots and action sequences can be quite blurry without the glasses, there are wide swaths of this film that don’t even blur the image, making it seem like the film is showing 2D imagery, rather than 3D.
In the case of Cars 3, there is an impressive amount of blur, but unfortunately it’s in very limited quantity.
Usually, the blurrier the image is, the better a chance the image is being conveyed with depth and clarity.
If you take your glasses off at any given point during a 3D movie, you should expect a bit of the usual blurriness to the images being presented.