Eh, I thought it was perfect. I hate how modern Pokemon games have become quasi-MMORPGs, in staleness of core design, lack of combat depth and also their desire to have you spend every waking hour doing absolutely mindless rote activities.
This was nice. Strictly superior oldschool Pokemon clone with fantastically punny names, really cute characters and a nice runtime that's still longer than the old Pokemon games but not as bloated as modern ones.
As stated my someone else, it is a fairly mid-sized game. The map is rather small, albeit with various vertical level that stays inaccessible until you catch specific monsters. But all of them lacks variety. You either get grassy plains, scarce forest, automnal forest, forest or water. Oh, and a mountain too.
But once you've got accustomed to the grass/forest part, it gets boring quite fast. I'd really like to get a desert/sand biome, a rocky one, and the likes. And they even have the lore excuse to be lazy with the placement, they don't even have to make it logical.
Cassette Beasts is relatively short. You can beat the story in a couple of days. 100% and the DLC take longer, but it's an absolute pleasure all the way through. Highly recommend you move it to the top of the backlog.