Delve - Not fun, rewarding, or challenging

Still haven't reached depth 100 but one thing comes to mind how they could have made delve feel more wholesome, rather than being a endless loopy grind of quick fastfood enounters.

Actually, I have zero info about cities or what you call them, what level they start to spawn and how to enter them, so maybe this is already in the game,
but I'll throw my idea out there regardless:

First of all, I want to explore, meaning decide where I go and find something interesting. This would include ancient cities/pyramids which at early depths
1-40 would be fully open and later on require more and more key/fossil artifacts or other indiana jones type puzzles to be completed in the surrounding areas to be unlocked.

There could be unique rarity encounters hidden away at the end of a very long one way tunnel, that you need to explore first, then you need to find the equally rare key to it, or complete a hard boss/challenge to open it, which would have some league specific uniques or just super high rarity loot, in the exalts. Or a legacy altar key...

So finding stuff would stay on the map and you could go back and work with it later on. Now everything is just *go go go* never look back, which is a big missed opportunity imo.

Imagine you find a rare tomb around 40, with lore and hints about keys to unlock it. Then at 60 find one key, and at 80 the last key, finally make your way back via the waypoint, complete the encounter and loot/unlock some cool shit that only few have done.

But instead we just grind grind grind azurite in the millions speed racing while shooting caffein into our veins. Noice.