I didn't used to have a problem with Mastery Level 6 & 7 Achievery

but when I realized that my friend with a fresh 25k mastery points on Zed has Mastery Level 7 on him whereas I have 151k in Yasuo and don't even have Mastery Level 6 yet.

It's hardly based actual experience anymore - two lucky games for at least an S- on a champion you picked up last month and you get higher mastery levels than the people who have spent years maining a champion seems really ludicrous to me.