I want to medium-to-heavy push back on this.
Techdirt didn't build a single point of failure into their revenue stream, otherwise the title of this article would be, "Why is Techdirt closing down?". Their support page[0] lists 8 different revenue sources other than Google Ads.
And this is precisely the type of diversity that you want. Signing up for 5 different ad networks isn't really good diversity, because:
A) your different revenue streams are cannibalizing each other (there's a limit to how many different ad networks you can shove on the same page), so you can't grow your revenue as you diversify,
but more importantly,
B) many of the factors that affect one ad network (ad blocking, political pressures and privacy laws, fundamental inability to moderate well) will affect all of them.
It's not good to have 5 different revenue streams that can all simultaneously be destroyed by the same event. In that scenario you've increased complexity, but you haven't gotten a significant gain in reliability. On the other hand, pulling in money from advertising, Patreon, merchandise, product commissions, and even Kickstarter campaigns means that no single event will ruin your site.
I think it's important for people looking to diversify income streams to think about what each new income stream offers, rather than just duplicating an existing stream X times. I don't see any advantage in having 5 different frameworks for serving ads on a single site. I see a lot of advantages from setting up a Patreon on the side and selling podcast ads outside of your site.
[0]: https://www.techdirt.com/pages/support.php