There are plenty Pokemon I don't like based on their aesthetics, but I can see what the design team were going for (even if it was a joke that might not have landed such as Maushold, it needed to be that way for the joke the designers intended) and the little touches they made, so it's just a question of preference even if I don't like them.
That said, Pawmi's line is the one line that really bothers me, because the subtletly of the changes are too big without a joke or lore that needs that subtletly to land.
Now, people like to say "Oh, look at $insert_older_pokemon_here, it also has few changes" or some other thing, when a little change can go a long way when you're strategic about it. Pawmi doesn't even have that.
All of those Pokémon (specially in different representations such as the in game sprites or in game models) have very different silhouettes, expressions and fire placement. Perhaps more importantly, Typhlosion (big, angry, upright) feels very different from Cyndaquil (smol, almost quadruped, placid) and Quilava is a midway transition between the two. Even if there aren't a lot of differences, they feel different and that's what matters.
Same thing here, color changes, yes, size difference, yes but you could even miss that and you'd still be able to tell them apart because of the silhouettes. Charmander is round, Charmeleon is full of sharp edges. Charmander is pretty much always smiling, Charmeleon is always either frowning or smirking.
Small objective design differences that compound to a greater subjective feeling difference.
Even Muk and Grimer have different depictions that telegraph the slight differences. Grimer is taller and thinner, Muk is shorter and squatter. Grimer has a goofy expression, Muk has an angry / put-upon expression. Muk's model / sprite / etc. is always in an attack like position, while Grimer is arms out as if it's going for a hug.
Muk and Grimer are one of the weaker distinctions because there's only so much you can tweak about about a basic amorphous shape and eyes (although they could have exaggerated more, like say, Voltorb and Electrode), although originating in a sprite media where you can fix a pose helped them a lot, but let's check out the Pawmi line
Can you tell the difference in the silhouettes? The pompadour gets scruffier and they get bigger, that's the only change to the silhouette if we put them in the same general pose. (There are other changes but they don't translate to the silhouette).
And because most people first saw those guys in a dynamic 3D environment where they were tiny compared to you (possibly in the distance), in similar positions such as walking or standing upright and in a variety of expressions (or where the expressions might not show up well because they're tiny). Maybe if they came in a 2D environment, the change would be more clearly demarcated like Grimer / Muk, but it's just not great design for 3D open world.
If there is a joke, I genuinely can't tell and someone please tell me because it might recontextualize the Pokemon for me and it feels like there should be a joke? Similar designs, similar names (even in Japanese: Pamo, Pamott and Parmott), it feels like it's riffing something but I genuinely can't tell what that riff is.
