Thanks for the suggestion. I gave it a try, but it doesn't remove the game's default quest markers - it only seems to do so for the ones it implemented itself. Moreover, it doesn't even display quest markers for newer zones like Vvardenfell or Elsweyr. Not that I'd want any additional markers, but to me that says the addon isn't even maintained anymore.
Here's a screenshot of the default game markers that I'd like to get off my screen, in this case specifically for the quest 'For Glory!':
