So developers have roughly 9 months to update their apps or they won't run on 5 year old hardware? This doesn't sound as devastating as some of the tweets and headlines would imply (that seems to be common these days).
Most of these applications are games, the developer may not even be alive anymore at this point and there's no ROI in updating working complete games just because they are old.
Your basic actual game (not the F2P/IAP garbage) just creates an opengl context and handles touch input, that stuff only breaks when the OS itself breaks core API, I've got many games from my early 3G/iPhoneOS2 days which still run fine on a 7 running iOS10 (though not all of them).
Complaining about one closed source company that is actively growing and managing the platform we rely on for increasing performance and security because other closed source companies abandoned their software seems rather confusing to me.
* an application was an early 32-bit iOS port; the codebase was not 64-bit clean at the time of the port
* elsewhere, the world moves forward: new DirectX APIs for the desktop, new graphics and asset pipeline techniques, etc. Development, accordingly, moves on; the application ships on other platforms, and large reusable sections of the code - the engine - have been updated, rewritten, made 64-bit clean, used in other applications etc; however none of this work was migrated to the branch for the original iOS port: at the time, that had shipped and was stable, large sweeping changes are expensive and risky, with (at the time) little visible benefit for an existing working stable iOS application to justify that.
* 2015: Apple pulls the rug out from under updates by mandating 64-bit support. The developer is faced with a stark choice: pay the porting cost to iOS again for the new codebase, or redo the 64-bit cleanup work from current trunk on the ancient branch (a cost comparable to porting again, at this point), or suck it up and say there won't be any more updates. Since the app is several years old and sales are down to a negligible trickle, the third option is picked - the other two are not affordable.
* 2017: Apple pulls the rug out from 32-bit-only apps by releasing an OS update that no longer runs them. Users that bought the application can no longer use it. The developer can't afford to update it or port it, but is (a) still selling it on other platforms and (b) is still using the engine in other applications that are selling, so would be crippled by making it open source.
Each individual decision is sensible at the time, but it all adds up to checkmate.
I'm personally aware of at least three developers that are in this trap right now.
All Apple has said is that it will remove apps from the App store that don't support 64-bit.
Journalists shouldn't make stuff like that up.
Older apps that users have paid money for a while back, that work and are in use right now, but that developers haven't received much income for in years since everyone that wanted them has already bought them, will stop working for users that upgrade their device.
Cue user complaints, but no extra money coming to deal with them.
Apple have unilaterally decided it's time to burn something; developers have roughly 9 months to choose whether it is their time and money or their users' possessions that get burned.