How do I delete duplicate imports from Photos without deleting originals from all my devices?

It looks like your iPhone and the Mac were both using iCloud Photos Library and are synced by iCloud. When you are using iCloud Photos on your iPhone and your Mac, it is not useful to import new photos directly from the iPhone. They will sooner or later be transferred manually by iCloud. If you import them by downloading from the iPhone as well, you will create duplicates. The import dialog cannot always recognise these photos as duplicates, because the photos downloaded from iCloud to the iPhone are new files on the iPhone. And Photos for Mac will see them as different files from the files that are already in your Photos Library on the Mac.

Try to wait for the new photos to download from iCloud to your MacBook, unless you have no internet access for quite some time. The use the Image Capture.app to download the photos to a folder on your Mac and import form that folder to Photos. This will have the advantage, that you can compare the photos to the ones in Photos and can import selectively the missing photos.

Why are you using iCloud?

If you do not want to need to keep the photo libraries on your devices identical, you do not need iCloud Photos. Save all your photos on an external volume, and turn iCloud Photos off. Then you can simply download the photos directly from your iPhone via USB and can delete the photos from the iPhone, that you already imported to your Mac and do not need on the iPhone.

Then you can sync selected albums to your iPhone to view the photos. The draw back will be, that the Live Photos will no longer be Live, when you sync them back to the iPhone, so you would have to keep the original Live Photos on the iPhone.