Firefox has a task manager now. They should improve on this to compete with Googles. Nobody wants to type a URL when they can hit an easy shortcut.

I have a hope of remembering about:performance. I can bookmark it, and it's there in autocomplete. You can make a link to it in your webpage or in a nice plugin (which, once it gets a couple thousand users, you can sell to an honest businessman for tens of thousands).

Shift-Escape? what? I'm supposed to just randomly press every key combination till something happens?

If you can remember the hotkey for Windows task manager, sure. It's Ctrl+Shift+ESC. If not, you can access it through the menu.

A shortcut is better than clicking the Hamburger menu icon, then "More" then Task Manager / typing it into the browser.

Why not both (if the shortcut is available)?