Let's be real for a second, Scooby-Doo movies are not high art, and that's perfectly okay. Thankfully the people over at Warner Brothers are aware of this and have never taken the franchise too seriously.
I've not seen many of these movies but this one was pretty okay. The animation looked like classic Scooby-Doo which I'm sure would please die hard Scoob fans, but it didn't really do much for me.
The plot is the standard Scooby-Doo affair, you can more or less figure out what's going on in the first half an hour. The main stand out of this film however is the humour. Velma's anger at a website font choice, Fred debating which net to use to catch the ghost, a 12 year old YouTube rapper doing a concert at a rodeo in a ghost town? Hilarious. It doesn't sound funny but goddamn most of the jokes land really well.
Unfortunately they try to cram too much into this movie, there were a bunch of throwaway gags and characters that served no real purpose and overall the story and animation were pretty bland.
So if you want a funny Scooby-Doo movie that you can watch with your brain turned off, go for it. If you're looking for something with an engaging western story, go watch High Noon.