I'm going to preface this by saying i'm a support main before anyone crawls out of the woodwork to say "lmfao adc mains so whiny". I'm playing adc currently to prove to myself that I can get to plat on a carry role; that i'm not just some boosted enchanter main who got lucky. I'm also not complaining because pyke "steals kills". The k's don't matter to me in kda, it's all about the KP and keeping the deaths as low as possible(although it is impossible to keep them low in some cases). Alright, with that out of the way, let's move on to the meat and potatoes of this post.
Basically, in lane pyke is fine. He plays out like a typical hook support. His w incentivizes him to roam, and that can cause some hickups when players don't know when to roam, but that's not really a big deal. His laning phase is standard hook support stuff. That's not the issue. His issue is outside of lane.
So typically, when you're playing with a tank support, at the very least they'll get some sort of item(knights vow/locket) or provide bare minimum peeling when you get dove. Enchanters are enchanters, and mages are on the backline with you, so they'll be doing their best to cc the divers and blow them up. Pyke does none of these things. Pyke lurks around the fight, looking for picks on the enemy backline. This often completely leaves the adc to dry. If the adc is someone immobile against an assassin or diver they're generally just done for. Defensive itemization like GA only delays the inevitable, since often the fight will shift the the enemy backline trying to kite away our team's diving. so there will be nobody nearby to help you
Overall, it's just an extremely unpleasant experience playing with a pyke outside of lane as an ADC. Yeah, I know I can just play ezreal, but I personally don't enjoy playing with ezreals as a support player, and I know a lot of my friends(who also play support) don't like laning with him, so I try to not play him. I just wish pyke had some sort of incentive to help his ADC out in fights.