Pyke was hit by the removal of Ancient Coin & Targon's allied healing, but he's always had much higher gold generation than the other supports. That's his thing. The offset is that he doesn't have many of the important things a conventional support has.
Senna was designed with preseason and S10 in mind. Also, I'm not saying Senna is weak but it's not like she's running around dominating the entire game and no other support is viable. Thresh, Morgana, Blitz, Pyke, and a handful of other supports can still hold their own.
Edit: God, the amount of bias here is crazy. I feel the need to explain myself.
I'm not arguing whether or not Pyke is strong or weak at the moment (although, since we're on the topic: if you look at any website from OP.GG to League of Graphs to Champion.GG, he is in a much weaker state) but pointing out that he did suffer from the support item changes.
OP claimed that he didn't get punished at all when he did, since his only form of allied healing was Targon's and he lost the advantage that Ancient Coin gave him. Whether you like Pyke or not does not matter: The answer to OP's post is that he was hit by the removal of certain items.
The term "conventional" is referring to things like allied heals, allied shields, and reliable CC. While Pyke is in a lower state than before, I do not think he's unplayable or incredibly weak. My point is not to call attention to how strong Pyke's current kit may or may not be, but to bring attention to the fact that the things he does have is not always what is needed and to show that he was hit by the support changes.