Q: How do i access the photos I've stored in the iCloud drive on my iPhone

I think they should be In your photo library (have you tried looking for them in your Photos app when connected to wifi?)

Use the iCloud Drive app on your iPhone to show you the folders with your photos. You can open individual photos, but not edit them like in the Photos.app.

Your photos would be much easier to browse on the iPhone, if you imported the photos to the Photos.app on on your Mac instead of to iCloud Drive, and then enabled iCloud Photo Library. That will also upload the photos to iCloud, add them to your iCloud Photo Library, and then download to the Photos Library on your iPhone. All Photos Libraries on all devices will be updated and synced.    iCloud Photo Library FAQ

Archive or make copies of your iCloud data - Apple Support

but the only way I can figure out would be to download them to my Mac mini and then import them into the Photos app, but that seems like an overly complicated way to do it...especially for an Apple product .

That's true, but iCloud Drive and iCloud Photo Library are for different purposes - iCloud Drive for documents and data, and iCloud Photo lIbrary for media files. They are using different services of iCloud.

If you enable iCloud Drive on your Mac Mini in the System Preferences > iCloud > iCloud Drive, the photos on iCloud Drive will download automatically.  You will see them in the Finder, if you select iCloud Drive in the sidebar of a Finder window.  You can then import them directly to your Photos Library.

If I'm in Photos and select "Import", the iCloud Drive is not an available source.

That is unusual.

I can select iCloud Drive in the Import panel for Photos.  Which folder are your photos in on iCloud Drive?

If I'm in the iCloud Drive viewing my photos, the only option I see when I right click is to "share" and I can select Add to Photos. When I select that, nothing happens.

You may not notice, that something happens.  When I am selecting an image on iCloud Drive and use "Share add to Photos", the Photos icon in the Dock will bounce a bit, and then the photo will appear in the Moments in iPhoto, sorted according to the capture date.

It is hard to find the photo in Photos, because it will not be added to the Last Import album, and also not appear at the bottom of the Apll Photos album. I have to search for the filename. But it will be imported.

In the Import panel click the column view button to be able to open the folders more easily.

And then click the folder "Users" to be able to access your home folder.

Did you ever configure your sidebar in the Finder?  To make your iCloud Drive visible in the sidebar, open the Finder Preferences and click "Sidebar". then enable iCloud DRive ad any other folder you want to access from the sidebar.