Was the mastery update good or bad for the game?

In my opinion I'd say no because they cause balance issues for champions. I'll list my reasons why. Feel free to discuss about them in the comments below but try to keep civil.

Masteries give stats. Items also give stats along with some giving a unique effect that can change how you play. Keystone masteries do the same type of thing except a lot more emphasis on changing the playstyle and less about stats. But items have an issue, not all items can be used to their full effectiveness on certain champions. (E.G. DFT being much better on and compared to most champions). If a mastery is super OP on a champion then what do you do? Do you nerf the mastery or the champion? This was the issue with DFT. It was incredibly good on non burst mages because of the extra damage, but it was insane on brand at the time. After the nerfs its almost never used except on niche picks like brand or Jhin (seriously. you get like 400 DOT burn with jhin. Its gross). In this case RIOT had to nerf the mastery instead of the champion or else always force that champion to take the mastery, no matter what. As a problem though now DFT does little to no damage at early ranks and is pretty much negligible. TL;DR the keystone masteries feel like 9 items, champions are forced to pick

My biggest point though is what the mastery update did for supports. Remember the good old utility tree? It had good stuff like XP boosts, gold per 10 boosts and other great things for supports. Getting the XP boosts on support was fine back then, you had to dedicate a lot of mastery points to be able to unlock the XP boost. Nowadays with the new mastery tree doesn't have a good spot for those XP and gold/10 masteries. All of the trees are used by all types of champions and its hard to balance an XP mastery when there aren't any good "support" trees to put it in. (imagine an ADC throwing points into the resolve tree just to get an XP boost and the same with the support).

these are my two main points. Have fun discussing!