For people who would like a more concise source (in ES6 & a bit of functional style):

    [...document.querySelectorAll("*")].filter(el => getComputedStyle(el).position === "fixed").forEach(el => el.parentNode.removeChild(el));

The code above also works, you can add the URL below to bookmarks.

    javascript:[...document.querySelectorAll("*")].filter(el%20=>%20getComputedStyle(el).position%20===%20"fixed").forEach(el%20=>%20el.parentNode.removeChild(el));

Also, for people who uses Safari:

You can add javascript: links to your bookmark by adding any bookmark & changing the URL.