How do I transfer photos on my iPhone to my Mac now that Photo Stream is gone?

iCloud Photos can be used to sync all photos between the two devices. see: Set up and use iCloud Photos - Apple Support

Or use AirDrop: How to use AirDrop on your iPhone or iPad - Apple Support and Use AirDrop on your Mac - Apple Support

Another option: Transfer photos and videos from your iPhone or iPad to your Mac or PC - Apple Support

There are also 3rd party options such as https://www.photosync-app.com/home and https://imazing.com/

You can connect your device to your Mac and transfer using finder or you can enable icloud photos on all of your devices to sync automatically.