As I have said before, I simply cannot understand why 'they' would not think that it is an important and, let's be honest here, most basic of basic options.
It is a design principle of Photos to avoid controls and options that clutter up the view. Photos offers plenty of predefined albums instead, so we should not need sorting options. Instead of one "All Photos" albums that can be sorted in various ways, we get several albums that are sorted differently. Instead of sorting one album we switch between albums to see the photos sorted differently. It is faster, because the albums can remain sorted in a fixed way.
Like you, I would prefer an orthogonal design, where all albums - predefined or custom - can be sorted and rearranged in the same way. And I would prefer to have more sorting options than just date and title. I would like to be to sort by the file size, the pixel size, the rating. Appel could easily offer these options on a mac.
There may be another reason why Apple is avoiding too many user interface controls, and that is iCloud Photo Library. One declared design goal for the Photos.app is to make the user interface experience similar on all devices - so Photos on a Mac should not be too different from Photos on the iPhone. But on the iPhone display is not much space for additional controls, if we want to be able to see the photos at all. So currently the design of Photos for Mac seems to be influenced by design decisions for Photos on iOS devices. See this comment in the user guide: https://www.apple.com/lae/macos/photos/
(emphasize added by me):
iCloud Photo Library gives you access to your entire Mac photo and video library from all your devices. If you shoot a snapshot, slo-mo, or selfie on your iPhone, it’s automatically added to iCloud Photo Library as well — so it appears on your Mac, your iOS devices, Apple TV, iCloud.com, and your PC. Even the photos and videos imported from your DSLR, GoPro, or drone to your Mac appear on all your iCloud Photo Library–enabled devices. And since your collection is organized the same way across your Apple devices, navigating your library always feels familiar.