Contrarians will always call there favorite starter/s the best and everyone else shit despite some being miles better then the ones they love, both design wise and power wise, nothing can be done about it.
But personally, I agree here for once. People will say that they look to humanoid, but really these are supposed to be fiction magical creatures, not real world animals, they don't and shouldn't follow the rules from our universe. That's probably also the reason why most fan made starters I've seen 99% of the time are "it just gets bigger" evolutions and looking more like Gen 2 starters with them being more animalistic and no flamboyant accessories, just coloured animals with super powers. And yet GF has been showing time and time again that they are done with the "animal" looking starters and by making them more like different RPG characters gives them a more unique feel (after all, you only get one in the entire game and no where else, might as well make them stand out from the bunch)
Does this mean that they can get away with bad designs and call them "original and cool"? No far from that, but it's just a trend that they have been keeping up with for three or more gens already, but the fans simply ignore it.
Also, as a side note, I don't think any of the Alolan starters are bad design wise, Incineroar is clearly the weak link, but it's passable. Decidueye has a fun theme going on and Primarina pulls the pop star theme perfectly. Incineroar also pulls the heel wrestler idea well to, but I can also see where the complaints come from and why it's a lot less popular (also, stop it with the quadruped thing, it's clear that it's never gonna happen)