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#21
That's what you should do if you want to do a thorough reinstallation of Firefox.
That will give you a new Firefox profile, in addition to the new installation.
If you delete that Mozilla folder, your bookmarks and profile will be deleted.
I'm not telling you to do it. I'm just letting you know that is the way to get a fresh start with Firefox if you choose to do so. You would have to back up bookmarks first.