That sure explains why every statistical website for league says he has some of the highest winrates and playrates in the game, as well as upwards of 57% winrate for those who get a good number of games in on him going up to 60%+ for those who play in the upper ranks of league as well as being a consistent presence in Professional play.
He is a VERY good champion and saying he is weak is just unintelligent. Coming from you who seems to like to play him in his ranked games, I can see that you must just upset and can't accept that you are either not very good with GP, or because of how many times you failed to pull off a combo because someone better than you disarmed your barrels before you could get it (a thing that virtually never happens to good GPs). Whatever your perception may be, GP is a VERY good champion who doesn't actually have an exploit.
He gets - cc removal with a %missing hp heal
- free movespeed for proccing barrels
- ranged harass
- fantastic waveclear after first item
- 2 aoe slows
- armor pen on barrels
Also, saying he is an easy gank target with 345 base movespeed with a 30% movespeed buff and the 60 movespeed from phage (which is a core component of his most used item) that he also gets on killing a barrel, as well as the 40-80% slow, this champion is not gankable by a well versed player. On top of all of this, the aforementioned "well versed player" would very often land his barrel combo before someone can disrupt the chain because of how people think (that being you want to focus on your own champion's abilities before another one's, and GP focuses on his barrels and timings while other players wouldn't do such NEARLY as often/ as quickly).
GP can play safe in pretty much every matchup a LOT more easily than other champions and to say that he can be killed by carry junglers is just not relevant because in the lane he can simply avoid them, and in teamfights he gets peel from his team if it's well put together.
The only real relevant counter to good GP players are champions with instant ranged autos like vel'koz or azir, and even then those champions don't often get played in the toplane.
This is why he needs to be weaker in the early game, to prevent people from just safely farming away until they get to their powerspike.