they try to create a sense of urgency to sell people what they don’t need.

Do they? Yes, they certainly advertise what's new but they're not primarily targeting customers with last year's phone. I recall seeing previously that the average time to keep an iPhone is three years. On Apple's iPhone 15 product page, I found two spots where it called out direct comparisons to previous iPhones: "A17 Pro GPU is up to 70% faster than the GPU in iPhone 12 Pro" and "iPhone 15 Pro has up to 6 more hours video playback than iPhone 12 Pro." They're targeting upgrades to the newest flagship at people with the flagship from three years ago. Of course due to the long support for iPhones, that three year iPhone will inevitably end up in the hands of another user, where it will continue to live on, so there's nothing at all wasteful about upgrading. It's not even wasteful to upgrade every single year because those year-old phones are still used. It's only when the phone is irreparably broken or hopelessly, legitimately obsolete (due to still rapidly-improving technology) that it's then recycled (and Apple has developed special robots to make extracting the rare earth metals viable at large scale).

I wonder what the latest iPhone would look like if Apple were on a once every two years release schedule instead of annual.

I think it would look exactly the same as it does today except that it would include two years' of innovations and changes rather than one, but would also mean that if you needed a new phone before its release, your only option would be an increasingly dated model. Customer: Hi, I'd like the latest flagship. Store: Here's the best technology that was available 20 months ago.

I also think it's worth noting that Apple pretty much single-handedly slowed the release schedule for phones. Prior to the iPhone, Nokia was releasing roughly a dozen barely-differentiated models per year, spread throughout the year.