Kalos was mostly a well-mapped region in my opinion (yeah, yeah, "amusement park" or whatever, but all but maybe three of the routes were fun to explore and the cities were so distinctively designed)—it's not THE BEST by any measure, but it's far from the worst as go regions by themselves.
The problem is everything else.
Almost none of the Pokémon interest me that much—I can name a few that I like (Vivillon, Espurr, Noivern, Heliolisk, Clauncher line, Skrelp line, the mascot Legendaries), but there are far too many that feel bland and Gen I-tier.
Many of them feel like their primary concept revolves around tacked-on elemental associations; for example, Gogoat is based solely on the idea of adding the Grass type to a goat, and Pyroar is based solely on the idea of adding the Fire type to a lion which gets bonus generic points because that's basically everyone's first Fakemon. That's not to say that they don't have distinguishing flavor on top of that—Gogoat has its riding thing (and connection to its rider through its horns) and Pyroar has gender differences—but the element that was tacked on has nothing to do with that and steals the design focus, and with Pyroar in particular, Meowstic did gender differences more interestingly in the same Gen.
Even designs people say are "literally my mom's x" in most other Gens at least use some clever word or concept association, like the oft-criticized Komala exaggerating koalas' inactivity and turning it into an actual gimmick, rather than using the type itself AS the concept. Komala is honestly one of the less appealing Gen VII Pokémon for me despite this, but the fact that even it does that better than some of the most popular designs in Gen VI speaks volumes.
