There is a "read mode" on Firefox for desktop and Android that does this? You can set the font face and size and then every time you open an article, just click the "read mode" button and it will display the article all nice and clean. Safari does this too on desktop and iPhone.
I use it for sites with so tiny fonts, it's impossible to read without zooming the page.
And content sites / articles that take forever to load on my slow bandwidth.
It even helps for sites that start playing videos automatically - wasting my precious bandwidth.