Buy it if you're ready to be an exceptionally patient pet owner. Watch some videos online otherwise.
Buy it for the excellent collection of built-in Nintendo-made levels. Get the Wii U version if you want to actually make your own.
Buy it if you want to take a relaxing trip to the great outdoors without ever leaving your home.
If you ever had a good time with a previous Rock Band game, buy it and remember what you've been missing.
Buy it if you can tune out the story for an interesting take on the open-world genre.
All in all, these missing features and changes for the worse are disappointing blemishes on what is still an incredibly enjoyable game. Mario Kart 8 isn't the best game in the series, but it adds enough new visual, gameplay, and track design flourishes to its well-trodden core kart-racing gameplay to be worth a look.
Sequel keeps the appeal of the original while making improvements at the margins.