Frustrations with Pyke balance wise and pretty understandable. Hyperbole can get tossed around, but he is extremely oppressive and anti-fun to play against. The argument isn't ever that he has no weaknesses, but that they are not comparable to his insane strengths, and his weaknesses are much more manageable especially if the player behind the wheel is remotely competent.
His kit is staggeringly overloaded. He has a number of mechanics that many agree are just plain infuriating to play against, as if Riot were memeing in the design phase, seeing how much they can put onto a single champion. Then they called him a support, as his ult roughly doubles kill gold and gives it to his carry.
His hook is one of the lowest cooldown hooks in the game, while maintaining significantly more strength and utility despite it. You can charge it while being slightly slowed, are able to throw it in virtually any direction at will, its hitbox feels janky due to it being a triangle and still having a box (though hitboxes are named that way for a reason), and deals non-negligible amounts of damage.
His W gives him a substantial movespeed buff (that scales with lethality for some reason) as well as camouflage. Circles appear underneath you when he is near, which only serves to perpetually zone his opponents as you cannot take the risk of getting close enough to see him and punish, especially as he can instantly dash and stun you or begin his hook charge up, which gains an advantage from stealth due to human reaction time.
His E is his dash stun (the 1.25s duration which also scales with lethality?), a high damage, decently long stun time ability that also enables him to close the gap. This move does so much, on just a 15 second flat cooldown.
Then you have his Ult, a true damage (though because it executes this really doesn't matter), %health execute, where the health necessary to execute scales with both his bonus AD and his lethality. It also blinks him to the center if it is successful, and it resets per kill. I can't tell you how many pentakills I've seen gotten just from smashing the R key onto a team. His ult has the same problems Darius ult used to, where it gave so much flexibility in usage that they had to significantly tone back his reset. I'm just waiting for when they do the same to Pyke, as its degenerate nature makes Darius R even in its heyday, look like Taliyah ult.
His passive enables him to do much of the bullshit he does. It makes it so he cannot get bonus health from items, which you think would be crippling on a squishy, but he hardly needs it. His base health growth is already pretty good, and bonus health is converted to AD anyway, making him even stronger in killing people. Honestly, this is strong on its own, and would be a fine passive.
But no, he also needs to drastically heal back 60% of his max health every time he is damaged merely by going into a bush or using his W. As, whenever he is out of enemy sight, he heals twice as fast as Garen for up top 60% of his max health. It does depend on the damage he takes, but like a Saiyan, the closer to death he gets, the more the heal will do. This health restore scales off of 800% of his bonus AD, so a Pyke with just a couple of items will always restore over half his health when heavily damaged.
I feel he suffers from the same issues as Tahm Kench does: overloaded kit that is difficult to balance around multiple roles. Both champs were designed with the support role in mind, while bringing very powerful tools to the table to enable them to do so. Unfortunately, their tools were so strong that they were able to succeed outside of bot-lane and did so with flying colors. Attempts at balancing one, would affect the other usually in the inverse. Pro-play is often the crux of these balancing decisions, which is problematic in its own right, considering solo queue is such a different beast that they may as well not be the same game.
Pyke is a very interesting champion in both design and lore, with a cool kit to boot. However, it's hard to look past how much he sucks the fun out of an entire game to see the nuance of his character.