iPhoto opens and runs just fine on my 2015 macbook air. Running latest High Sierra. Seems to take longer to open and close though than it did with earlier versions of MacOS, but has always been slow. My photo library of 58000 images is on a usb3 external 1T drive.
IMHO the replacement of iPhoto with the much poorer featured Photos is just one example of Apple's neglect of the Mac systems.