No one is asking for perfection. An average marketing team at most companies would have had something on shelves for DADHAT. It's not a wild creative leap to think of doing so, and it simply isn't nearly as hard as everyone defending WotC makes it out to be to create a few extra pieces of art for Golden Vault featuring the DADHAT characters and have swapped them in (which can be done very late in the publishing process, assuming they're the same size as the art that ended up being used, which can certainly be dictated to the artists) once the early test screenings showed -- as they did -- that the movie would be well-liked.
Likewise, Stormwreck Isle, which featured the cartoon characters that didn't actually appear in the adventure could have easily instead have featured the DADHAT characters in the art. Heck, they could have re-released the exact same box in a "DADHAT Special Edition." (Although I would have gone the extra mile and written up both the cartoon characters and DADHAT characters as level 1 premades to include in the box, myself.)
Honestly, people act like creating D&D content is like splitting the atom. It's not that hard, and it's super-weird that so many people want to insist that no one could do it better than WotC, despite them stepping on rakes on a monthly basis for the past year.
This goes double for the people furious about Spelljammer, who clearly don't believe that WotC are infallible, except strangely when it comes to marketing.