I'm tired of hearing about this. A Pokémon not being on four legs isn't a real problem. And I know it's not a real problem because they're not popular.
Let's take a look at some of the most popular Pokémon from each generation. Charizard. Gengar. Tyranitar. Gardevoir. Lucario. Zoroark. Greninja. Dragapult. Tinkaton.
Not only is not a single one of them on four legs, most of them are anthropomorphized to appear more humanoid. And I'm not an expert on anything, of course, but changing Pikachu's design to appear more expressive and human-like, and less short and round, was obviously a good thing.
We can use Butterfree as an obvious example of this. It's a humanized butterfly, with it's little hands and feet and with a human-like facial construction. Whereas in real life insects often have hairs and feelers and tendrils and bristles, those features can be kind of off-putting, so Pokémon tends to smooth those features out and apply a lot of stylization to avoid them becoming too "real" and therefore predictable and/or too creepy.
The big exception to this would be Eevee and it's evolutions. Now, the problem with Eevee is that it's pretty unspectacular just on it's own, what makes it so interesting isn't Eevee itself, it's that it can evolve into potentially anything.
This was clearly intentional. It's not supposed to be anything all by itself, vaguely a cat, a dog, a fox, it's meant to be familiar but unspecific, something you might recognize but it's ambiguous.
This isn't a bad thing, but as the alleged co-mascot I'm... whelmed? In that context it really is the "sad beige millennial" of Pokémon. And you can also see this reflected in the Litten fan-evolution redesigns, where it evolves into nothing, the most boring and predictable route you can possibly imagine.
Incineroar on the other hand, is *very* expressive and memorable and filled to the brim with personality. I would even argue that it's the most Pokémon-like of all the Pokémon designs. It's almost like they looked back on a lot of the reoccurring Gen 1 design sensibilities and then placed them into a more modern context.
This was something they tried to move away from a little bit in Gen 2, where many of them applied far more softer, animal-like features to the designs. There's also not much depth to them, too defined by the animal they are portraying with not enough influences from another reference.
But this is where Gen 3 comes in, which has Blaziken, which is awesome. Therefore, I can rest my case. There's nothing to be disappointed about, you're just operating on the sunk cost fallacy at that point. You're BORING!!!