Why are boss unique's unnecessarily shite?

Sry here is a little rant.
I did full power kulemak like 30 times now, 20 of those with 110 IIR even.
What i wanted was a Scattering Calamity Staff to play a build that works but only with a very specific setup, meaning that the staff is not that great to begin with. The specific staff has become very expensive, as always when someone posts an interesting build.
What did i get out of my 30 or so kills? No Level 20 staff, no jewel.
Since i cant afford 50D for an item i bought a whole bunch of unrevealed staves and wasted a whole bunch of Echo omens. I did like 12-15 staves, did i hit calamity? yes, did i hit Add proj? yes, did i see damage per life or mana once? no. (And yes i also reforged even more to maybe get another level 20)

So you have a staff which is not very good at like 50% drop chance, then you have the possibility to get lvl 18, 19, 20, i assume 20 is like 5% chance? Then you get to unveil them and all you see is a bloated mod pool with the chance of seeing spelldamage per life at like what? 5-10%?
Now you can see why theres not that many and the ones available are very expensive. Why is a build defining item which is not even that great so impossibly and unnecessarily hard to acquire?
Its basically the same story with the rings, a whole shitton of bloat.
You know, i used to think endgame bosses should be exciting, but for whom are they actually exciting? The peeps who go there and hope to get somehting useful? Prolly not. The only reason Uber Elder was a bit exciting in PoE1 was because they dropped watchers eye, it might not be good, but at least you occasionally drop something that is potentially very usefull. Why were the other uber bosses worthless? Cause you have a 1% chance to drop something that might not even be good if you get the wrong roll.
So how is this lootdesign fun for anyone? Its not because so many items are unavailable for most players cuz they cost a shitton because you think 1% is fine, totally worth doing the same boss like 50 times and never getting shit? Much rewarding.
How about making pinnacle bosses actually exciting and rewarding by having reasonable drop chances and not this convoluted triple barrier chance close to zero to get something you actually want. Cuz that would be to much fun? Cuz regular peeps would actually be interesting in doing these fights apart from atlas passives?