I think you are endowing the developers with omniscience and infallibility when they have neither. Things change during development, sometimes based on feedback (Weapons didn’t even have different weapon speeds until 2+ years into development, perhaps due to the feedback that weapons needed such features.). Maybe they weren’t thinking about using the keyed dungeon system to make the campaign more replay-able as well, but if they are truly listening to feedback then the ideas in this thread might allow for change mid-development in designing the campaign to allow this down the road if they think it’s a good idea. Giving feedback earlier gives more time to accommodate that feedback if development hasn’t gone too far down a road that disallows it.
I have no idea if the ideas in this thread are good or not; I think they are fairly easy to implement, but I might be wrong. Regardless, they are relevant. At the very least it expresses the desire of some in the community to have a replay-able campaign as a part of the endgame equation. And that is super valuable feedback even if they don’t decide to act on it.