It was great to have a setting that was different. The mystery didn't sound different but New Mexico is a great backdrop for a mystery like this. Loved it when the franchise expanded its locations in number and in variety from primarily Season 3 of 'The Scooby Doo Show' onwards, and this aspect was always revelled in without being culturally insensitive. The latter of which could be further from the truth in "New Mexico, Old Monster".
Which is a very good episode and better than remembered. It is another one of those episodes that doesn't have the most exceptional or unique of plots, which was dismissed by me as forgettable on first watch, but is memorable for the location, its energy, the character moments and how it approached the material (primarily the humour). Which helped make it feel different, without being too much so as it is still unmistakably Scooby Doo.
Have no issues with the animation, which is very colourful and beautifully varied. While unmistakably contemporary Scooby Doo, it was great for "New Mexico, Old Monster" to have an old Scooby Doo feeling to it too. Especially the setting, which is reminiscent of something like 'The Scooby Doo Show's "A Bum Steer for Scooby" (am not crazy about that episode as an overall whole but love the setting). The music is groovy and atmospheric. The voice acting is all fine.
Some of the funniest writing of Season 2 is in "New Mexico, Old Monster", with it having a Looney Tunes and Jonny Quest feel to it at times. The "old Anasasi had a farm" gag is hilarious. The opening immediately grabs the attention. The monster is memorable in design and is pretty frightening, really do wish that its real form wasn't so easily telegraphed well before the finish though. Absolutely loved the episode's energy and the colourful supporting characters.
Which does make up for that the mystery is a little thin and not that hard to figure out.
Really liked the episode on the whole. 8/10.