Instead of worrying about what's not in the game, enjoy what is in it in my opinion More animals will come in time...
As for crocodiles, there are two in the base game, which is pretty good (If they had more I'd expect to see lots of posts about how 'they're all just the same' - I want more variety - waaaah!)
I do agree that prioritizing some less known animals did sorta backfire. While its one thing to say "I think penguins are more important" or "I think leopards are more important" I think we all can agree that Penguins, Jaguars, Polar Bears, Kangaroos, White/Black Rhinos, etc. are all far more important than the Aldabra tortoise, aardvark, nile monitor lizard, or Nyala. More animals the better, but not at the cost of what are essentially basic zoo animals now being likely sold as DLC. Now will they sell? Of course, but I can see it sewing some discontent with Frontier that I'm getting a polar bear, but now needing to shell out some extra money to do so.