This feature has saved so much grief and wasted time and focus. It is native in Safari, and if it is also in #firefox, i haven't yet seen it or learned of it.
If there is a popup live video you can hide it and then look at the website without the anchored noisy video.
If there is a phony 'your desktop is infected' popup with an invisible frame blocking the whole page, it can be selected and eliminated.
If this feature was to be amazing instead of just integral, it could include crowdsourcing and the ability to subsribe to other's lists of hidden components. Of course there would be a privacy focused way to do this so its not like people can see that someone is blocking lots of popups on foxnews or whatever.