I get that, there is other zoo scenery that you just place down, but is necessary component of zoos.I think with the no substance he means that you cant really do anything with them aside placing them down.
Like i too would like more sizes and stuff, but at the end of the day the exhibits are basicly little more than a scenery piece
I haven't built a zoo without a reptile house, for example, and shallow roster of exhibit animals in combination with rigid dimensions of exhibit boxes gets a bit stale.
More variety in exhibit species and exhibits themselves is perfectly reasonable ask. It's not a top priority for sure, but it's popular topic for a reason.