Photos took 3 hours to import 10 pictures, and several of them were duplicated.

I wonder if what you're experiencing is due to a caching issue. Have you tried restarting the Mac in Safe Mode, which clears out system caches.

Start up your Mac in safe mode – Apple Support (UK)

Note that starting in safe mode, and the first time you restart after, will take a little longer.

"My device setting for Photos is to Keep Originals, so it's not creating compatible versions."

What do you mean? Does "device" refer to the iPhone or your Mac?

Are you referring to the "Download to Mac or PC" setting on the iPhone or the "Setting > AppleID > iCloud Photos"?

Is either the iPhone or the Mac or both syncing with iCloud Photos? If you are using iCloud Photos on your iPhone, you should not even try to import from your iPhone via USB, as the primary storage of the photos is in iCloud and not on the device. If iCloud Photos is enabled, the photos will just be mirrored on the iPhone and the duplicate detection will not be possible and you may be just downloading a random selection of currently mirrored originals. Then use only iCloud to download the photos from your iPhone.

Some users reported, that the download from the iPhone will be very slow, if the iPhone is enabled as a personal hotspot. if you are using the iPhone as a personal Hotspot, try to disable this in the Settings, when downloading photos from the device. I can confirm that the manual downloading from my iPhone is much faster, if the iPhone is not used as a hotspot.

SupremeExecutivePower wrote:

I would love to upgrade but the phone wants another 3 GB of storage to do that. Guess what’s taking up all my space? Yep - photos!

I may try using the MacBook, just to follow “best practice” but c’mon, am I to assume no one ever transferred a photo until 16.3.1? LOL

Have at, then. I store my photo library on Mac, and sync from there.

As for glacially slow transfers, I’ve seen that occasionally over the years (not so much with USB-C, more commonly lots of photos and USB-A), but I’m also generally not running devices near capacity.

Running an iPhone or iPad or Mac near its storage capacity—with little free space—doesn’t work well.

I have seen cases of bugs fixed in updates. Which is why I’d suggested the update.

Update to iOS 16.3.1 (current), as a potential fix?

It is ludicrous and not at all typical. Something is going wrong. Restart both Mac and Phone and try again.