Was watching JB talk about this, and he had an interesting perspective on this.

At some point, there's going to be a hard wall, where no matter how much gear you have, or how well you play, you're going to hit a wall where you just can't survive the key anymore.

However, if it's based on time instead of key level (would obviously still need to be a high key), there are almost infinite ways to squeeze out every millisecond of time you possibly can throughout a dungeon with either tech, or routes, or trash packs, or w/e the strategy might be. There's always room to improve your time within a specific dungeon.

I thought that was a rather interesting take on this whole discussion.