In the darkroom, I selected individual negs to print. In PS I select individual files to work on. Lightroom seems to be designed to work on all the files at once.
It's not. It can, but there's nothing about it that makes editing a single file problematic or difficult. Select a picture in your list, hit D, and you're "developing" on that single image. Hit G to go back to your gallery, and find another image you want to edit.
You can bulk edit things, if you want, but there's nothing to force you to do so.
I think my favorite editing feature is just wrapping up a lot of disparate changes to a single image and being able to apply those exact changes to other images, without having had to preplan doing so. If I have a bunch of images where I'd like to tweak white balance, exposure, noise reduction, all the same way, I can edit one, arrive at values that work well, and then just copy and paste those changes to the other files.
With PS, if you use multiple tools to make multiple changes to a file, then you have to plan ahead in order to move those changes to other files. Start recording an action, make changes to one file, arrive at what you like, then stop recording and play that action back on the other files. Or you have to save and load presets for every Levels, Hue/Sat, or other similar operation you did.
I can't plan ahead like that: I often start down a path of editing before I realize that I might want to make these changes more than once. Then I have to decide if they're complicated enough and precise enough that I want to go to the trouble of recording them for playback, or saving presets, and back my work out to start it over. And forget going back to an image and figuring out what you did the first time. Even saving layers of changes doesn't tell you what you did to make that change.
Even the active history states don't tell you what you did: they don't save operation information, they merely save pixels. A history state will say "Levels" but there's no way to find out what you did in that panel. All you can do is flip back and forth and see approximately what you did.
And if all those operations were specific and temporary (valid only for the photos you just worked on), then you have the detritus to clean up, of presets you don't want to keep around, actions you don't want to save, etc.
This is not an attempt to change your mind, if you just don't like Lightroom. I just want to make sure that there's no misperception of Lightroom's virtues or vices. It has got problems, but it also fundamentally has some capabilities that, while achievable in PS, involve huge workarounds and generally a loss of process information.