Yeah, iOS 16 was a disappointment on that front. I was hoping we could set our own dark/light mode switching wallpapers. That way I could at least download old Apple wallpapers from the internet and set them manually. Maybe in iOS 17…
Well, technically with Shortcuts you can. You can basically create and easily switch themes manually or automatically with Shortcuts. And technically you can always download the original files of the wallpapers from a Google Photos album and set them. Apart from life wallpapers it really doesn't make a difference.