Full tank build on assassins but still kill anyone in 1.5 seconds or less.... RITO PLZ

Isn't anyone else getting tired of the fact that they can be working hard at actually becoming skilled at playing a champion to its fullest extent, only to get run the hell over every time someone decides to face smash their keyboard to kill you, no matter what you do? By this i am mostly regarding how thoroughly not fun it is having to deal with assassins that build FULL tank but can still kill pretty much anyone in less than 2 seconds anyway. Whether it's the items, the champions, or both, I believe this is a serious plague to this game. Why can an ekko or an eve or an alkali be allowed to have the ability to kill someone almost instantaneously without building any damage items and then be tanky enough to stand there spamming laugh at an adc or apc that's blowing all their cds and aa the hell out of them only to have them continuing to spam laugh until they FINALLY drop to, say, half hp then just burst that carry down with no effort at all? THIS DOESN'T MAKE SENSE AND IT IS NOT BALANCED. It's not fun for anyone except the few that decide not having to put effort into their gameplay to win is the best thing ever. RIOT please do something about this nonsense. It has been going on for FAR too long.