I agree that ads aren't a great solution, but the entire reason Mozilla is doing things like that is to avoid having all their revenue (and thus their existence) dependent on Google. How else do you think they should make money?

It's also worth pointing out that the included ads are targeted locally on your computer, and none of your browsing data gets sent to Mozilla (https://help.getpocket.com/article/1142-firefox-new-tab-reco...).

And it's also really easy to turn them off (preferences > home > "sponsored stories").