PBNs did always work and Google is far from inventing some magic wand to devalue them, but like all things in SEO, the easy wins and shortcuts that existed 10 years ago are gone. Today you need excellent content, solid onpage optimization and quality links, no matter if it's natural, paid, PBN, whatever links. The whole SEO industry became a lot more professional, mature, data driven. There isn't any secret knowledge any more, no hidden loopholes.
So, is it harder to build and grow a successful site today? Yes! Do PBNs have less effect? No, but your PBNs have to be better than the PBNs of your competitors.