Easylist will contact you, strongarm you into disabling your countermeasures and threaten to block all JS on your page if you don't comply.
So no ad servers can load, no prebid, nothing will function/load if the user has an adblocker that uses easylist (all of them) installed.
I'm still not entirely sure it's for the best or not.
On one hand, it is a concentration of power into hands a few people.
On the other, it is for a good cause, to maintain a list of ad network and site banners that drain resources, cause privacy issues, etc.
The Easylist people aren't saints. They get paid off by Google to allow "Acceptable Ads". So you just show a different campaigns if your user is running adblocker nowadays.
Just that Easylist is indirectly funded by ad revenue (google)
When it comes to ads, it's about the bulk of people, most don't run anything other than the default lists.