Android 5.1.1 was released in 2015. In technological terms, this is ancient history. Users searching for "YouTube for Android 5.1.1 Top" are usually in one of two situations:
Google officially discontinued support for Android 5.1.1, meaning you must rely on older application packages (APKs), lightweight third-party players, or mobile web browsers to access content. Why the Standard YouTube App Fails on Android 5.1.1 youtube for android 511 top
If you prefer a dedicated native app interface without using a web browser, look toward lightweight frontend clients built by the open-source community. Android 5
If you want to get your old device up and running, let me know: Why the Standard YouTube App Fails on Android 5
If you prefer a dedicated app interface, certain community projects have developed ways to keep YouTube running on Lollipop.
For an app-like experience, tap the browser's menu button (usually three dots) and select This creates a shortcut icon on your desktop that functions similarly to a dedicated app.