The Daleks rarely change appearance actually, and never that dramatically. The first real change in Daleks doesn’t happen until the late eighties, and it’s very minor, and is because of story reasons. The cybermen change much much more...but all of these, and the Borg, are in some way mechanical. Change is logical. Batman? Adaptations. Otherwise we may as well talk about regeneration in Pride and Prejudice.
There are changes in biological races in SF and Trek, but it’s usually either (a) a refinement of existing designs and makeup (like worfs appearance) or (b) after bumping from a relatively minor first appearance to a recurring set up (Odan to Dax) led by production wishes. Contradicting 45 to Ninety minutes of stuff for production reasons.
The original change to the Klingons in TMP, and their evolution through the films and TNG fall under both of these in some respects...contradict three or four episodes of TOS in a five minute sequence in TMP, but squint and it makes sense (and gets ENT to sort out the loophole. Much much later. But that illustrates that DSC should know it’s going to cause a bump in the road. It has before.) followed by the redesign for Kruge and Co because they are going to be on screen much more in TSFS, but keeping it in lineage with what came before. We see this throughout, until Worf in TNG is literally wearing an old Klingon sash from TOS. There’s a continuity.
DSC has time to build the continuity back in, and in some ways these are new paradigm Klingons (to go back to the Daleks.) because not only are they a radical change, but they are a radical change that on some levels just doesn’t work, are mocked by some, and disliked by some. Enough of those ‘some’ add up to needing to walk it back a little (the same on the ships, perhaps more so.) because it’s an avoidable mistake for various reasons. This isn’t a refinement, or a riff on design language already established, it’s a bit of a mess (even the new Batleths are too overwrought.) created by either too much control at the top, or a lack of it, and a mess in communications between departments. That and our familiar face off judges just needing to prove themselves and going waaaay too far.