Fire types have always been rare. It's not like DP is that unique, it just has a bit less compared to other games.
Look at gen1; the only Firemon you'll be using realistically are Charmander, Flareon, Vulpix or Growlithe. And Vulpix/Growlithe are version exclusives.
You can catch Magmar and Ponyta too, but those are at Cinnabar Island. That's pretty much the end of the game; after that, aside from sidequests, the only content left is Gym 7, Gym 8, Victory Road, Elite Four. Magmar and Ponyta are the equivalent of post-game mons in gen4, it's just that gen1 didn't have a post-game.
