Deleted photos not syncing across devices.... (iphone and Mac)

When I take the time to delete photos from Photos on my Mac, it says "this will be deleted from all devices" of course.... but it does NOT. And vice versa. I'm having to delete photos twice, once on iphone and once on macbook. this is AWFUL because digital decluttering is hard. :)

I know that "photo stream" is gone (or whatever) but surely I'm not supposed to have to sort through 5,000 photos and delete them TWICE?

Why aren't photos/videos deleted in both places? Thank you!