Let's imagine these features are extremely effective and widely adopted, and the advertising market evaporates. What do people think is going to happen to the content ecosystem - suddenly all the low quality ad sponsored clickbait will disappear?

Personally, I think if the only way to earn a living is to convince people to pay for content, we will see much more polarization as consumers self select into their information silos, and producers are incentivized to produce content that flatters their readers sense of superiority and/or aggrievement.

Probably a lot more UI dark patterns such as the “Click here to read more” embedded inside an ad, login pages embedded in ads, etc. Can’t erase that stuff if you want to get to the content. And of course the immortal ad that randomly decides to move around the screen.

Check out those illegal live tv streaming sites if you wanna see how bad this can get.

You can commonly block elements with ad blockers, e.g. ublock

Sure, but it's not exactly user friendly to get it to work site wide, unless I'm blocking something simple like a graphics file by name.

Having the browser use machine learning to write the equivalent of a Greasemonkey script for the site with an easy way to revert changes would be much more user friendly.

There is an element picker in ublock

If you don’t want to wait, the iOS and Mac AdGuard apps already allow this. It’s very effective and I use it semi regularly to hide support chat popups and signup forms.

There are probably other apps with that feature too if you don’t like AdGuard

I use AdGuard for this too, it's great.