Did it count when Trills changed look and how the symbionts worked between TNG and DS9? Has there been an explanation for why the Romulans changed their brow makeup between TOS and TNG, but unlike the klingons when a Romulan showed up in Star Trek VI, he still had the Vulcan-style makeup? But in Enterprise, the Romulans had the TNG-style makeup?
There are valid criticisms of Discovery, and it's perfectly fine to dislike it. But anyone who's complaining about how it doesn't fit canon is ignoring all the times the incarnations of Trek they do like ignored or arbitrarily changed canon.
I think the complaint might better be approached by the question: Does the change make it easier, harder, or the same in terms of the actors delivering lines, moving smoothly, or...y'know,
Acting in the makeup.
The TMP/TNG style with Klingons didn't significantly degrade the actors' ability to deliver an interesting character, deliver their lines clearly, emote, perform athletic movements and stunts, etc. etc.
IOW, it didn't make it harder to see them as characters, rather than rubber suits.
Now...Discovery...
the changes are horrible not because they're changes, but because the makeup's so heavy the actors are no longer credible as the characters they portray-they're in "Gorn rubber suit" territory. Fight scenes become boring, lines are delivered flat (and mispronounced thanks to the oral prosthetics), the 'character' is stripped off leaving only some very expensive makeup and prosthetics.
THIS is
the problem with the change. It's compounded because while the props are heavily detailed, even ornate, they've lost that fundamental that Klingon gear had before-that is, a utilitarian build. The armor they're given is hard to move around in, and looks like something from a fetishwear outfit, their bladed weapons h ave gone from 'weird but okay it can work' to 'you can't hold it without pointing a sharp bit at yourself, and can't use it credibly or effectively except to kill yourself." The armor has lots of depressions that act as shot-traps, guaranteeing a wound will most likely be directed inward at your vitals, (look it over).. Then we get to disruptors with sillyspikes added that aren't useful in melee, provide no benefit in ranged fire, and make carrying it a practice in being really careful not to stab
yourself. In a culture that commonly uses melee fighting, the new version dagger has a grip that will become slippery when wet and a grip shape (for a species with four fingers and a thumb, laid out like human hands) that increases the awkwardness.
this is not "improvement", the changes don't make them more detailed, or more credible, or more threatening. Instead, the changes make them more generic-rubber-suit-spacemonster-aliens, built to be easily defeated by the protagonist (even to the point that in the second episode, Michelle Yeoh's character basically had to jump on T'Kuvma's dagger to get stabbed.)
the changes to the Bajoran eyebrows made it easier for the actors to play the role, the change to the Ferengi was a deepening of character and culture, and made them easier to use as depth and setting characters rather than monster-of-the-week. the changes to the Trill also made it easier for actors to act and play and develop characters.
teh changes ST:D did to Klingons make them harder to play, and thus, shallower and less interesting as characters, because they have nothing but 'word of god' that they're even capable of sentient thought.
further, they've been stripped of pretty much all characteristics of Klingons as developed in prior series save one-they're ridged and like to fight. Unfortunately, this is the single most
generic villain-alien trait you can have.
in short, they're
boring. They're boring, because they've been raced right into mediocrity, they're generic and flavourless, flat and uninteresting, only cool in publicity stills.