The back button lost very useful function: if you held it down, it would show the history for the current tab, allowing you to skip forward or backward in history. It saved time (and data) getting to the page you wanted to be on, and was indispensable for getting past redirect pages.

Now, there's a forward button in the menu, which can only go one step forward at a time, the back button, which now only goes one step back at a time, and the browser history, which includes all tabs, not just the one you are currently on.