What about dive routes? That's a unique type of environment that was completely axed from the later games. It's optional in the sense that you can just, you know, not design dive routes, but at that point everything is optional. Furthermore, the argument that GF won't do something because that's not what they have historically done is flawed. They used to include the data of all existing Pokémon so far in their games, remember?
Again, not saying it will happen, just that they've made drastic cuts before, and the wild area still feels like a 'testing the waters' kind of addition to me.
Its not just the wild area though. Pokemon on the field, messing with encounters from entry to entry
The entire core of the series is built on finding ways to mix up how to find and capture creatures. Its a natural and logical progression
There is no way to trend away from this