They can’t stop improving their product because some users don’t want to update their devices. What they should do is release an update that will prevent the use of v4 on devices that don’t support it. Display a message to user indicating they either need to install v3 or upgrade their device.
This is where they failed, in my opinion.
FYI…you can still download v3 from app store and it should be stable on older devices. It just won’t have the latest features.