removing the promotion on the dashboard if a player already tried it.

I honestly pay so little attention to them, like the ninja on mixer thing, just not an issue to me

It's a form of advertising, and although it may not be of interest to some... we must accept it until the next advert takes its place. Not unlike those which we constantly see in our daily lives via TV, newspaper, magazines etc..

Unfortunately i dont think you can remove the promotion or ad, but it would make more sense for them to remove the promotion off your dashboard when you've done the promotion already.

Cant even use https://support.xbox.com/en-US/xbox-one/console/customize-your-home

You can be more Specific about what your ensues? I Suggest if you have a Personal Insues you go to Feedback and Report Session on Handbook and go to the Link and make a report

if you mean the ads, you can't