I have this problem too. I have tried every fix mentioned on the Internet and none have worked consistently. This is a significant issue for many users and APPLE is neglecting us. For those of us that use this feature regularly, it is a real problem that APPLE doesn't provide a proper fix. Many on the Internet suspect that APPLE is trying to force us all into using iCloud for all Photos storage and that seems diabolical and unfair. To simply provide links to articles that send us back around in a circle is even worse.
Today I restored my iphone 12 Pro Max to factory settings, with all updated software. I have rebooted my Macbook Air 2020 M1. I have basically followed every possible instruction and I have NO PHOTOS ON MY IPHONE. Yet, Photos is still stuck in the "Preparing to import from iPhone..." screen. I have waited up to 10 minutes at a time. I have rebooted several times (both iPhone and Macbook Air). I am really really frustrated. This is a company where we pay extra to not have to deal with this type of treatment.
APPLE - Are you listening? Will you fix this problem once and for all? All it takes is a quick Internet search to see how many different forums this has come up on and how many different users have expressed frustrations. I have counted at least 20 different ways that people TRY to get this to work, but not many people are successful on a consistent basis.
PLEASE, PLEASE, PLEASE - An issue like this is a serious black eye for you and a complete waste of HOURS of my time, not to count the hundreds of other users over the years with the same problem.