I mean, you totally have a point, and probably aren't wrong. The villains are probably the tougher sell, though at least for me, I think I may want the villains more than the gang themselves. We've gotten versions of the gang over the years- albeit none as good as these- so they feel less crucial in a weird way. I mean, they are the show, after all. But also, there doesn't really feel like as much of a point to them, at least for my display, without a bunch of the iconic villains to surround them. Some of the more generic ones as well, you can easily work into a display or photoshoot for other lines as well- the Mummy certainly, as nothing about it really screams "Scooby Doo", per se; maybe even Captain Cutler as a generic spooky diver.
Knowing nothing of how Jada works, I'd assume they could perhaps recoup a bit of their cost on re-releasing the gang members in different colors. Shaggy is a super easy repaint for the red shirt version, and I'd assume you can re-use most of Scooby's for a Dum, etc. Of course it's easy for me to sit here and say what Jada should be doing, but from an outside perspective, it at least feels pretty easy, if it comes to it.
Who knows- maybe they just spent so much time trying to figure Scooby out that they're a bit behind on the villains, and so, while technically part of the same wave, they'll get released separately from Scooby, so at least we'll have Scooby ready to go along with Shaggy. I ain't giving up hope just yet; it was a whole lot of radio silence before we even got these, and as we know, Jada does things on their own schedule.