The rewrite of the Oompa Loompas is different for two reasons: it was Dahl’s own rewrite, not performed by a soulless corporation; and it made the text better, not worse.
Even an author’s own revisions can be heavily criticized when they diminish the quality of the original work. Witness the Star Wars special editions, which aside from making questionable edits to dialogue and pacing, also jammed in incongruous CGI effects that stick out like a sore thumb, making the films feel inconsistent, and though perhaps the CGI was cutting edge for its time, in retrospect those effects have not aged nearly as well as the original effects, which were cutting edge for their time.
The Puffin changes are similar in kind. Roald Dahl as an author is known for his dark humor and misanthropic themes. Throwing in a moralizing sermonette in The Witches (whose eponymous witches are bald) that “there are plenty of other reasons why women might wear wigs and there is certainly nothing wrong with that” is unnecessary and inconsistent with the tone of the original work. Meanwhile, Dahl’s own moral points are obfuscated or eliminated. Dialing down Augustus Gloop’s obesity interferes with his purpose as a lesson on gluttony; cutting out Mike Teevee’s obsession with guns dampens the consequences of his obsession with television. George Kranky’s grandmother was such an unpleasant person that she was never really missed after he murdered her—well, that point’s not made anymore.
Then there are more minor changes, unremarkable physical descriptions that are apparently no longer acceptable coming from a mainstream publisher. Describing Miss Spider’s black head, or Earthworm’s lovely pink skin. Scared people who are white as a sheet. Tall skinny Bean and dwarfish pot‐bellied Bunce. What once were colorful descriptions (often literally) are replaced with bland unremarkable alternatives, not because anyone of consequence took offense, but because whatever company the publishers contracted this “modernization” task to wanted to justify its paycheck.
And the worst of it is that the rightsholders are the ones doing it. The Bowlders who first Bowlderized Shakespeare were resoundly made fun of for their delicate sensibilities, but I don’t really take issue with them, because they were just a family sharing with others how Shakespeare could look according to their tastes. No adult was deprived of Shakespeare by the Bowlders.
The situation is different here because had it not been for the vociferous outcry you complain about, the originals would no longer be available to anybody. Due to the public response, now they’ve said they’ll continue providing uncensored versions (whether they’ll keep that promise remains to be seen). Had readers shrugged and moved on, the censors would have won, and we would see these changes more and more throughout the publishing industry. But now maybe there’s a chance that this trend will change direction: that the industry will regain its faith in normal people to read books from another era without having to be coddled.