Except he isn't? The logic of "he's just a blitz clone" would also apply to thresh, he pulls you, CC's you. Except thresh is better with lantern, so blitzcrank is now useless. Oh hey, Nautilus, he has a hook, more cc than thresh, and more mobility, so now thresh is useless. Do you see your failed logic here? These champions aren't exactly the same and have their own uses in different scenarios. Blitz is useful for his hook e combo. W and ult are hardly considered when talking about him. Thresh has an amazing hook, awesome peel, and a knock back, plus his wall slow. Naut has a good hook, self shield, large aoe slow, and guranteed knockup.
You know where pyke becomes unique? He has a hook that can be melee range to do more damage, or be a flip at close range. His w is a STEALTH, his e is a delayed stun that sets up with q really well, his ult is an execute. And his passive encourages a more selfish/hit & run playstyle. You don't understand the fact that, while the abilities serve similar purposes, they are mechanically different and therefore cannot be directly compared. Different mechanical differences, regardless of the end goal, mean that different use scenarios occur.