Meh, I'm used to it. Dated more than a few of those in my time.
Biased, of course, because it features DC Comics' Scarecrow, but "Happy Halloween, Scooby Doo!" was a lot of fun. You get cameos from Elvira and Bill Nye, a fun intro, some clever gags, fun action, etc. It's a little overstuffed in places, admittedly, but hectic in a fun way. I believe it also takes place in the Mystery Incorporated world, or at least something adjacent to it, since Crystal Cove is mentioned (there's also a tiny Pup Named Scooby Doo reference). Without spoiling anything, it also ties together a couple other Scooby movies released around the time as well- Return to Zombie Island and Curse of the 13th Ghost; it's not entirely necessary to watch them, since (I don't believe) it's hinted at in those that there's anything overarching, but still. You might be a bit underwhelmed by the culprit- that seems to be the biggest complaint- but it's still a really fun time.