What is slowing down Firefox?

Are you still even on Firefox? I moved a long time ago to Chrome as my main browser but I still use Mozilla Firefox because if its unique add-ons that are not for Chrome.  Well, if your still on Firefox you can disable some add-ons to make your browser as fast as when you first downloaded it. Mozilla has released a list of the add-ons that have an impact on their browser.  Below is the top 6.