Good post, sums up my opinion well.
It's sort of on the cusp of being a theme park, but the sparseness of some parts stop it from fully getting there.
I think its fine to have the big lawns etc for picnics, but they sort of need a bit more to unify it, and the structures can't just be pool fences and council type shade structures.
To me, a theme park is something that takes you away from the here and now, and when i was there, there's not quite enough to disguise the "Perth aridness"
If you wanted to fix that, the lawn itself needs to become its own semi secluded precinct, with a few structures in there that unify it...Heck you could even theme the area as an "aussie bush retreat" .
Then the fringes of the area get landscaped to separate it off.
The green area is more tiki themed shelters, and a layer of tropical gardens, fading into wild western at the western end.
The purple zones would be more of a classic main entry statement for the park. Do something with the paving here to make a distinc first impression.
The red zone would be gardens to segue into the Abyss/Rampage/Goliath area.
(And by the way, that area needs to be given a proper name....Eg "The Mythical Way" or "Land of Legends" or whatever)