You sound like one of those people who was venting years ago when Zyra, VK, Lux, and Brand started getting played as support.
The support position doesn’t need to be a marksman protecting wardbot every game. They can have fun too. Some people like enchanters (and protecting people). Some people like mages. Some people like tanks. Pyke and Senna are about making the 0 income position fun for a wider range of people. Thresh has a similar purpose when he was released years ago.
If your complaint is balance, that’s fair. Senna prolly needs some nerfs. It looks like you’re saying she and Pyke shouldn’t exist however. I can’t agree with you there. League is much better for having variety within roles.