Felines has always been the focus, but it was first in FeralHeart Canines got their own model that so many people wanted. It makes sense the game creator decided to make this a game that focused on both. To my understanding there's just more canine liking users out there as a whole, but of course the mileage might vary depending on which place you actually look directly at. If you like a certain species more however, a few rough edges on the appearance of a certain species shouldn't keep you or anyone away from still playing as your favorite animal, fursona, or characters.
Personally I am a feline user in the game, but as far as the thread goes I don't really create that many characters either since I just feel home on one. I Don't think I ever even made a canine and used it in the game so I'd most certain take part in the feline crowd. Why I personally enjoy feline characters is because that's where my heart is at, where other interests and activities has been linked to for some time but also being stuck in the lion king fandom which glues me stuck to animated lions. Felines just appear more graceful to me and playing on FeralHeart as one never felt odd or like I should switch to a canine.
In that way FeralHeart is very interesting too since it's a place where more feline only users and canine only users actually play the very same game together more or less, it creates very interesting situations.