Apple isn't here, just fellow users.
Nothing has changed on your device. You've simply used up your available space in iCloud and/or on your device. If you've filled your device, you'll need to delete data. You need not use iCloud and you need not keep all of your data on your device. The release of a new phone has no effect on the storage available on your device; it's fixed at whatever it was when purchased. Delete app data, offload apps, delete permanently photos and videos to free space.
When new devices are released some features may not work on devices that do it include hardware to support the feature. But, Apple continues to support devices for a long time, much longer than competitors.