The issue with droprates is how rng works at individual level. All the droprates usually is calculated based on: how rare you want the item to be * how many active people there are in the game * how many runs do they do every single day and then average it out. This works in mass scale but alot of unlucky individuals suffer from it.
If every player uses their own seed to generate the rng numbers, it means unlucky ones have lesser amount of "win" numbers in their rng seed or they are at the very end of the line. If all players uses the same seed, other players can "steal" the good drop right under your nose.
What I mean by stealing is, let's say a hypothetical situation with 4 players. We take a seed 1 and the first 12 numbers inside it are 0 0 0 0 0 0 0 0 0 1 0 0. They do 3 runs. after clearing each player rolls the loot number in order. first 8 numbers are 0's so first 2 runs give nothing. On clearing the 3rd run, since it's done in order, player 2 is the person who gets the good drop and others get nothing. Doesn't matter if the 1st person has never gotten the drop, that's how it works. So in this case even your party position matters as to who gets and what.
When you do this in mass scale, it's not distributed with the playerbase equally. Only way to fix such is by adding a system that would eventually guarantee you a drop. The rng system is not bad per say, it just has a tendency to be unequal towards the playerbase, leaving some people with nothing.