The thing that Lightroom really got right was not trying to mix all this stuff and organizing the master files well, so it was extremely clear where source material lived. I certainly don't want to root around thumbnails and previews in randomly-named folders.
Aperture's interface could have been great with some decent performance, and some of those decisions seemed to have survived with the iPhoto Library. Perhaps one big-ass ball of mud works fine for consumers with small file sizes and no archival strategy, but it's too prescriptive for me. If they brought Aperture back, and incorporated Photoshop-like features, that would be interesting and cool, so long as they left photo management alone.
The lesson I took a long time to learn was to not have the RAW processor import your files and instead get Photo Mechanic to do it instead, because it does a better job, and just use the RAW processor to process RAWs.
XMP/ITPC has been around longer than I've had a digital camera, do you know why Aperture didn't make use of those?