Braixen and Delphox definitely received criticism, and doubly so because of the bipedal shift. Delphox I feel still gets some hate, but people have certainly come around when it comes to Braixen. It's inclusion in Pokken, from what I've heard, was likely due to its tremendous popularity in Japan.
All that being said, while I like Delphox (though I like Braixen more), I think Poppliovely blows it out of the water designwise. It's actually my favorite final Starter Evo since Samurott in terms of aesthetics.
Delphox has inspiration from witchcraft and shintoism, I honestly see him as gender neutral, but we'll I live in an urban area with loads of bats, owls, tzentzontles, Zanates, snakes Owls, Parrots, pidgeons, vultures, foxes, coyotes and occasional heloderma suspectum that we call scorpion lizard as well as big fat rats and an occasional bunny in the green impact zones so I'm kinda exposed to their behavior in an urban area.
Foxes are one of the most badass animals, they even try to open cars if you leave food inside! Their calls do scare loads of foreigners since it's like a woman screaming, but they show how though the species is and how amazing they are at finding food outside of hunting, I can't see a fox as nothing else than a resourceful badass after growing up where I did, throw in magic and I ended up in love with Delphox, the eeveelutions and Ninetails never got me enamored as much as this wand wielding fox(outside of leafeon, wich sadly sucks ingame).
Gender is defined by the environment one grows, I grew up with foxes opening cars or chasing rats in packs while hiding in the riverside whenever a light went up, so I can't think of them as female at all, even after seeing a fox den when I was little, little fox are timid yet cute BTW.