I've seen this criticism(?) in many posts and in many forums regarding lens IQ.
What does this mean? Can anyone explain it? If a lens isn't sharp, doesn't render well, has soft corners or ugly bokeh... THAT I can understand. When someone says "clinical"... does this mean it's TOO perfect? It doesn't have the tiny, unquanitfiable flaws that lesser (better) lenses have?
What's a lens designer/manufacturers to do? Purposely muck up something in the lens so it isn't judged perfect? If I was a designer, this sort of comment would drive me bonkers.
My take - Nobody knows, so they keep repeating the term because they've heard it elsewhere. Perhaps it's a subconscious thing, the images aren't quite as attention grabbing as we'd anticipated. Maybe better PP would help, perhaps some selective blurring or saturation? Too flat? Add some vibrance.
Maybe longtime photographers are used to tiny flaws that (they assume) gives a lens "character". When presented with a sharp lens with great micro-contrast, it looks objectionable. Me, I'd much rather start with "perfect" and then have the latitude to later spice it up as the image warrants.
When I hear that about a lens I am using, I want to say "Ok, I'll spray a tiny bit of WD40 on the front element. Will that help?"