iphone15 bluetooth will not pair with other iphone

You also don't use Bluetooth pairing between iPhones and Macs.

The two work together through other means, like iCloud synchronization, synchronization through e-mail accounts, and Continuity features ( Continuity features and requirements for Apple devices - Apple Support ). Some of those Continuity features use Bluetooth, but generally not in a pairing way.

iPhones cannot pair with other iPhones over bluetooth. It's never been supported, and it's by design, so there is nothing to resolve.

What exactly are you attempting to accomplish by paring them?

Most things that require bluetooth between 2 iPhones do not require they be paired, just that bluetooth be turned on.

I have been reading in this Forums that there are many like myself who cannot pair their iphones.

There is nothing to resolve, you cannot pair two iPhones with each other, it's not possible.

I don't quite understand your question. What exactly are you trying to pair? Your iPhone 15 to what? Or are you asking about an iPhone 8? I have an iPhone 15 and have no problem connecting it to Bluetooth devices such as speakers, AirPods, etc.