Unfortunately, that is how RNG works, but everything equals out in the end.
I'll give you an example, User A can get 2 shiny pokemon in 1 day, while User B hunts for 2 weeks and still don't get a shiny.
User A has encountered 5.000 pokemon and got 2 shinies and User B encountered 12.000 pokemon and got no shinies.
Lets say that both players play this game for an absurd amount of time, and both players get to 820.000 encounters, both the User A and User B will have approx. 100 shinies caught, give or take few. When you look at the bigger numbers, you see that almost all results become more or less the same.
There isn't such thing as "account luck", all accounts have the same rates, of course the RNG is different for everyone, it is self-explanatory (**Random** Number Generator).
Most of the players in short-term hunts experience what we call an "average RNG" which is just an average on the probability chart, but there has to be some extreme cases when you look into anything that is recorded with only a fraction of the data needed for the "average" results. Extreme cases start to fade away when you collect more and more data. Someone can get really "lucky" in 1 game event, but that person can get nothing good in the next event, in the end, everything evens out.
I hope this clears out some things for you.