Lol.. this new lockscreen is no special magic that an iPhone 7 couldn‘t handle it. Apple just don’t want to support it anymore. They made a mistake (from their point of view) to support the 6s that long. So they ditch the 6s and 7 together that people will upgrade.The iPhone 7 doesn't have the necessary hardware required for the lock screen part of iOS16, and maybe even some other parts, which is why it isn't supported.
I have an 8 on ios 16 and really there is nothing special about this lockscreen. You can add some more stuff on it but for real. No reason to ditch the 7.
the 7 plus runs better on iOS 15 than an 8 on iOS 15 because the 7+ has 3 gigs of ram.