The reason why Riot always keeps champs like zed/lee sin in meta
Because they have counterplay.
I hate zed. I hate lee sin. But I'd much rather have slightly more difficult champions to be strong than stupidly simple champs to be strong. You know what wasn't fun? Being chased by a pre-nerfed Cinderhulk Sejuani. She is going to ult you, lunge at you, and kill you. When I'm being chased by a fed lee sin I can at least try to dodge his Q and have a possibility of escape; I can at least get a qss or zhonyas against zed to increase my chances of survival.
Are they fun to play against? No! But there is at least something I can do to outplay them opposed to just "avoid getting near them all game"
grab
and
are kept in the meta because of flashyplays, they jump around and riot likes that, so they make sure they stay relevant.