I'm not sure that the app economy wasn't a temporarily bubble. We've yet to see many apps reach the sustainable part.
Very few apps are successful charging the customer. A few games are successful selling in-app purchases, but even those almost never last. Social apps some times get popular but rarely find a way to monetize, they wind up selling themselves to larger businesses who use them as a loss-leader.
Compared to desktop and the web, the number of sustainable businesses on mobile apps is depressingly small.
that is, by definition, not a boom. A boom is a period of unusual, unsustainable growth. The boom is over and the app market is shifting into a normal sustainable market where good products and services are valued and low-effort or less useful apps have a hard time succeeding.
The headline wasn't "apps are dead" - just because you misunderstood it doesn't make it clickbait.