Gee, sounds like maintains these sites is hell. It also sounds like a huge opportunity if a startup could convince sites they need the fastest ads.
It's not the publishers! They all know our sites are slow, but like pornel said they don't have a say in how efficient their partners/advertisers code is. And they aren't going to rip that shit out and go broke just because people complain.
Ad block and the browsers sunsetting Flash is slowly forcing the ad tech people to change, but it's not near fast enough. In the meantime publishers revenue suffers and people continue to blame _them_ for the experience.
The alternative is they don't do display ads at all and go down the BuzzFeed route, where advertising is indistinguishable from actual content.
If you think it's easy to fix with technology, you are more than welcome to try.
There are also lots of very hard constraints. The publishing process is complex and on strict schedules, especially if it's connected to printing of a daily newspaper. There are hundreds of people involved, so upgrading CMS for a newspaper is like changing wheels of a car while it's moving.
And on top of that monetization on the web is hard. Users hate paywalls. Nobody wants a mobile app, especially not for overpriced in-app payments. But something needs to bring money, and even getting ad inventory that's higher class than "doctors hate this!!!" is also a very hard work.