In that case I would go for challenge mode in jurassic difficulty. The mode I could tell is different enough from sandbox and campaign mode as the level of income and storms is harsher in this playthrough, it should be more to your tastes if you like the challenge more than the building of the park, which does get easier as you could get so much money after your 3rd species of dinosaur in standard campaign mode.
Dinosaur packs will keep coming, it has been a post release cash cow to make more dinosaurs to keep support of this gaming going. I love any inclusion as I am a large dinosaur nut and would appreciate a new asset in my parks. But I do agree that there should be more buildings/attractions to be introduced into the game. Those buildings are what makes park building more interesting. My favorite so far is the paleobotany lab as it makes selecting dinosaurs for each exhibit more limiting, which makes it more fun.
I would love more buildings like these. Or different attractions at the very least. Gondola lift, 360° view tower, balloon ride, underground view. These are some attractions I could see come into the game that would expand more than simply new dinosaurs. DIfferent buildings = different layouts of the parks, leading to more interesting park ideas and concepts.
But yeah, I would recommend playing with challenge mode to get those skins, try out a map and see if that makes things more entertaining.