This weekend I read up and watched a bunch of videos (mostly the Angry Photographer) about how, in general, more lens elements results in a loss of micro contrast information and, as a result, a much flatter-looking image with more visible noise.
This is the reason why prime lenses tend to produce better quality images, because they have fewer lens elements, which means less processing of the light before it hits the sensor, but it seems like not many people talk about this outside of using nebulous terms like "3D pop" or "Zeiss pop" or whatever. Everyone's always talking about minor vignetting and corner sharpness as weaknesses to zoom lenses, but this is a much bigger issue in my opinion. I couldn't quite put my finger on why the 24-70mm zoom lens I have been using for a few weeks produces images that, while plenty sharp, just look "off" and a bit flat. Trying to look this is up is what took me down this rabbit hole.
Anyway, there's an experiment that can easily illustrate this. Take a photo of a scene with a lot of range (dark interior with contrasted with bright outside, for example) and expose for the highlights. Do the same image with the same conditions on a zoom and a prime at the same focal length and then take them into Lightroom. Convert them into black and white and then adjust the exposure, shadows and highlights, etc. until you get an image in which everything looks good and apply the same settings to the other shot.
It should be very clear which photo was taken with which. The prime's image should have far more shades of gray to everything that give it that feeling of depth or 3D-ness. You should also see less noise/grain in the darker areas that had their shadows boosted.
This was a pretty eye-opening experiment for me and is definitely going to make me consider the number of elements when looking at lenses.