Some folks are going to complain no matter what. Some of them are going to be vile about it. This is the Internet. Trolls gonna troll, bring fire damage.
That doesn't mean WotC gets a pass for doing a bad job. I agree that they are not to blame for the printer screwing up*. They are, however, to blame for a) not publicly addressing the issue once it became clear that it was an issue, and b) telling a distributor that they aren't going to reprint the missing books. Anyone who put in one of those orders has every right to be mad at WotC.
(On the "not reprinting the books" thing, I debated whether that was being fair to Wizards, since we are getting this information secondhand and paraphrased. But as of now, that is the only communication from WotC that anyone seems to have gotten; so yeah, I think it's fair to put that on them. Getting out in front of a highly visible screwup, even if only to say "We are aware of the issue and we are working on resolving it," is customer relations 101.)
*Well, probably. If they've had problems with this printer before, or if they switched to an unknown new printer right before the big 2024 release, then they are to blame. I wouldn't think either of those would be the case, but who knows.