I have no issue with visual retcons, because it's always been clear that we're not seeing on the screen "Trek as it happens" but "Trek as dramatized for TV."
A good example of this is the universal translator. Although the device is, frankly magic (no universal translator would work without being able to read minds) even if you accept that it still makes no sense as shown on the screen, as it not only translates dialogue, but makes it so the lips of those speaking an alien tongue match the translated speech. This is because we aren't seeing exactly what is happening in the "real world" of Trek, but an approximation of it.
Continuity errors are another matter entirely. Aside from the practical issues with the Klingon makeup, I dislike the redesign not because it's different from past shows, but because it goes against numerous elements established in the past.
1. DS9 decided to make it clear that TOS-era Klingons actually looked different from Berman-era Klingons
2. Enterprise provided a canonical answer to this with the augment virus,
3. Lots of minor elements of Trek stories made it clear Klingons have hair (the legend of the Sword of Kahless, Worf's adoptive mother talking about him growing out his hair, etc).