Masteries are POINTLESS
Bronze players can have that seemingly coveted rank 7 mastery (case in point, me at the moment).
All you need for it is to farm and give 0 fucks about teamwork.
It is not an accurate indication of skill.
You hard carry and get an A or whatever it doesn't mean a damn thing. All that matters is that you won and get to climb up the ladder unless, of course, you're playing norms.
And when you do get that rank 7 mastery, all it is, is a shiny emote you get to flash just to try and tilt your enemies. But then they can just mute you for being a complete dick and carry on like you are nothing more to them than a bot.