While you're developing a game, there's going to be a lot of things that won't be coded yet. Many of them are simply going to need to be stubbed in until you can implement them fully, or somehow worked around.

Which ones get what treatment is going to be very particular to your game, and your development style. There's no wrong way to do it. Do what works for your situation.

Yeah imo it’s definitely worth prototyping the core gameplay without the proc gen — not only does it let you test faster it also lets you experiment with features and designs that you may want to include in your generator without having to code them first.