I think it's unfair to put so much blame on Rovio. Apple themselves have done a lot to discourage traditional single-purchase apps and encourage IAP and subscriptions. For example, the App Store still lacks support for free trials (outside the context of subscriptions) and upgrade pricing.
Differentiation between business models is also needlessly hard. Apps that are free with most features locked behind IAP, free with ads, and free for a limited time with subscription all look the same at first glance in the App Store and there's no way to filter on business model.
Differentiation between business models is also needlessly hard. Apps that are free with most features locked behind IAP, free with ads, and free for a limited time with subscription all look the same at first glance in the App Store and there's no way to filter on business model.