This functionality has been baked in Firefox for a long time and I use it quite often. Not only makes the ads and other clutter disappear, but it also removes most of the "disable your adblock" unclosable popups.
It is definitely one of the super-nice things to have baked in straight in the browser, and probably one of the major differences I see between Chrome and Firefox in day-to-day usage. I just wish that somehow it was persistent for certain rules, but I can see how that is a slippery slope.
Not only the readability mode of Firefox is awesome, but they've also opensourced it separately, in case you feel you can submit a PR for a persistence of some kind or create your own extension that makes use of it.
https://github.com/mozilla/readability
I use it profusely along with Puppeteer in Node and it's an awesome building block for web scraping!