Apple has been dropping older subsystems and backwards compatibility layers long before app subscriptions were the default way people got paid for software. The 68k -> PPC transition happened in the mid 90's and 68k support was dropped entirely somewhere around OS 8 and the start of the iMac era. The Carbon framework might have been the most long running one, going from about 2000 to 2012 for deprecation and basically ending once the 64 bit transition happened around 2018. The PPC -> Intel transition, including the original Rosetta emulator was ~2005-2011. The app store itself only debuted in 2011.
I do agree that Apple does this in part to force developers to either stay active and maintain their apps or stop shipping for the platform, but I personally posit that the move of more and more apps to subscription models is simply due to how many more apps are connected and user expectations for update timeliness (and the devaluing of updates both by increased popularity of "free as in beer" open source apps and also the distribution of no-cost OS updates by Apple. People expect more for free and expect it as soon as someone notices a problem. I think the idea of not only waiting a year or more to have new features or some bugs fixed and then on top of that having to shell out more money for that is just not something people are as wiling to do. So subscription models become necessary to fund the continuous work that goes into keeping up with all the new trends. Apple's dropping of old libraries and frameworks is part of that churn, but it's only one part in a sea of other pressures driving the subscription model.
Losing carbon support on the Mac, and 32-bit support on both macOS and iOS was painful.
I particularly miss games like Chaos Rings 1&2, which are no longer playable and don't seem to be available anywhere.
Another bad change was when iPhone "backups" stopped including apps, which now have to be re-downloaded (which does not work for apps which have been removed from the app store.)
I do agree that Apple does this in part to force developers to either stay active and maintain their apps or stop shipping for the platform, but I personally posit that the move of more and more apps to subscription models is simply due to how many more apps are connected and user expectations for update timeliness (and the devaluing of updates both by increased popularity of "free as in beer" open source apps and also the distribution of no-cost OS updates by Apple. People expect more for free and expect it as soon as someone notices a problem. I think the idea of not only waiting a year or more to have new features or some bugs fixed and then on top of that having to shell out more money for that is just not something people are as wiling to do. So subscription models become necessary to fund the continuous work that goes into keeping up with all the new trends. Apple's dropping of old libraries and frameworks is part of that churn, but it's only one part in a sea of other pressures driving the subscription model.