Personal experience:
I've been a jungle main since season 4.
Since season 4, I climbed each season to Platinum, with about 60% winrate, on Warwick (1 Million mastery on him)
This season, I did climb to plat (then got back to bronze because transfer to NA and back means you get Plat --> Bronze overall), now in gold 2.
But I had only about 52% winrate playing jungle, much lower than before. And playing jungle feels AWFUL especially since the last patch jungle change (scuttler spawn later, etc). I had soooooo many games where I give a HUGE early lead to my team, like 3 infernal drakes + rift herald, good ganks, etc.... but then somehow I lose. I feel like it's the coin flip: who's got the better carry, when I play jungle.
So I started playing mid (after maining jungle and OTP ww for 5 seasons), and over 80 games I am 60% winrate, and even when the team is behind I can carry and it is much, muuuuuuuccccchhhhh less frustrating.
Jungle this season, and even more so since last patch, is awful garbage.
Maybe it is because Match Making is so fucked (at least in my elo, around Platinum), that basically the laners will have a huge skill gap. So it doesn't matter if you give the lead or not, the better carry will win the game. So to win, you need to play carry. Playing support or jungle this season doesn't work, because "giving an advantage" to a much worse carry won't help. You'll give them 6 free kills, drake and rift herald, they will still be half cs behind, and they will give shut down gold by getting outplayed our getting caught for no reason. Or maybe the jungle nerf (gold, exp) makes it that you're far behind laners, I don't know.
Fact is, statistically, I win much more by being the carry myself than giving advantages to my carries this season, in my elo.