I think you missed the point of “behavior enabled by design”. Of course I can remove it, as can someone who just stepped into a pile of poo clean their shoes. We’d just prefer that the pile of poo didn’t exist by default.

Targeted advertisements like the ones built into Firefox's new tab page are the exact kind of thing that privacy-conscious people like to block. When I recommend Firefox to a less-technical friend or relative and suggest that they use uBlock Origin or another powerful ad and tracking blocker, it's awfully ironic that the default new tab page is full of targeted advertisements. It's purely perception, of course, but it's the kind of thing that almost certainly isn't helping Firefox compete against Chrome.