Why do we keep changing runes masteries?

I was wondering why did LOL keep on changing the masteries and runes? Atm it feels like these new so called "runes" ain't even runes at all but hard scaling masteries where it just makes the game 10x harder to play? Most players and friends i know got frustrated and end up quitting as a result to changes of runes and masteries not for the first time in many years i had played. I as a player just don't understand why there must be such changes as in removing one major aspect of the game to add something else to completely changing the game style. It's more of a feedback than a question tbh. So I do not wish for a response or anything just question why. If anything we would prefer more modes instead of removing and adding runes/masteries.