But the Klingons have ALWAYS changed across the decades of the franchise's existence. You've got the first Fred Phillips version with swarthy skin and bifurcated eyebrows. You've got the second Phillips TOS version with just beards ("Friday's Child," "The Trouble With Tribbles," et al). You've got the third Phillips TMP version with a single vertebral-ridge running down the middle of a smooth forehead with ridges on the bridge of the nose.
You've got the Burman Studios version with individualized bony forehead plates and smooth noses, and barely any ridges on the females (i.e., Valkris). You've got the Richard Snell version with subtler individualized forehead-plates, also with much subtler female-ridges. You've got the Michael Westmore version with large, individualized bony plates and nose-ridges, and with no gender dimorphism in plate-size.
And of course, other species have been repeatedly redesigned, too. Tellarites went through 2-3 makeup variations in their three onscreen TOS appearances (later background Tellarites lacked the sunken eyes and three-fingered hands, and the dead one in "The Lights of Zetar" didn't even have the nose), then went to a more porcine look with less sunken eyes in Star Trek IV: The Voyage Home, then underwent a massive redesign in ENT.
Andorians have had multiple designs across TOS, TMP, TVH, TNG, and ENT, with many variations of antenna-shape, size, and position. The Ktarian makeup design changed completely from the big arched forehead-ridges in TNG: "The Game" to just a few tiny horns in Voyager (because they needed a simple makeup to put on the baby and child actors playing Naomi Wildman). The Borg underwent a major redesign in Star Trek: First Contact and beyond. And so on.
This is just something Star Trek *does*. It's not like Star Wars, where every tiny detail is religiously recreated. It's always had room for new creators to reimagine its look, to put their own stamp on it. There's nothing happening here that hasn't been done multiple times before across many, many decades. It's just that today's fans are already used to the older changes, or weren't there when they were first made. The new changes always take more time to get used to, and far too many fans mistake novelty for "wrongness."
But keep in mind that the whole driving philosophy of Star Trek is the exact opposite of that -- that the new and different are not wrong, that they're something to be sought out with open, welcoming curiosity.