Create an web application(a product of our company). Manager insisted on using X third party API instead of Y third party API.

Now the app is complete.
*Very slow, Shitty User Experience *

I feel shameful for creating such a disaster and also wasted 3 sprints on it. But couldn't do anything because I don't have an authority to take decision which API or technology stack I should use.

Business head and manager had a meeting. Now they want to use Y third party API.

So they called me for discussion, lets me know we will now use Y third party API and it should be completed within a week because we just need to change the API calls in code that's all, despite of knowing all the core logic is built around those API.

Don't know how to react to this :( Want to hit my head on a wall