He's outshined by pretty much every mid laner. His waveclear is meh at best unless you want to ult minions. Everything he does cho'gath does but better except in one regard. And that's the ult. fiddlesticks ult can be way more devastating.
fiddle has some glaring weaknesses which can be exploited to hell and back in the current meta. He isn't a tank killer which is kinda what is needed in the current meta. He isn't going to 100-0 an enemy carry unless he is just insanely ahead. In a lot of games you will be up against two or more tanks which fiddle really can't do anything about. He can't escape them or break through without his ult and his ult is quite honestly easy as fuck to stop.
In a 1v1 duel he will win most of the fights against anyone who isn't building tank if they don't have a way to get away and break his tether drain or a displacement.
I like middlesticks and I have some good memories of that magic bird flying way off into the distance for a kill. He is a strong champion but right now he's just outshined hard. Most of the meta midlaners have either tons of waveclear, dashes, or enough burst to delete him and usually a combination of at least two of them.
His time will come again but right now it just isn't the time.