Why am i not having fun with LoL anymore?

Why am i not having fun with LoL anymore? is it my age? (20) have i just grown out of it...? There is something about this game that has always compelled me to keep playing, and it was the fact that if you got good enough at one champion, your skills could become a work of art, legendary like many players i don't need to mention. I went by the philosophy that if i worked hard and put all my focus on the particular craft, i could be just as amazing or better...So i actually put in the time, i sit now as a 740.5 K mastery Vayne main, a ridiculous amount of time dedicated to a craft that has gotten me no where. (mas i ever achieved was gold 4, now im stuck in silver). I find my self losing lane every game to players who barely have no time in to the champs they are playing...i get it that shes suppose to be late game, but im repeatedly getting shit on with no hope since season 6 started. between the bork nerfs and increased cost, to vayne W rework that ruined the game for me, since then i can't win lane unless the support is the determining reason for the win. I'm not sure where to go from here, i feel like my main is useless and idk if i should just switch mains or quit playing all together, the longer i play this game the more tired of Annie and Master yi i get.