I feel your pain…!
The greyed out tracks can be re-activated by doing a “relink” operation. @Slak_Jaw explained how earlier in this thread (February 22, 2024).
Basically you have to re-import your “giant” folder as linked files in the “Files” section. Then you add all those linked files to a dummy playlist in “My Collection”. You can delete the dummy list after relinking. Now the tracks should no longer be greyed out.
The big problem with this work flow, is that on iOS/iPadOS you can’t just point to the root of your “giant” folder and import recursively. You have to go down into each subfolder that contains audio files and add all to the dummy playlist. Very impractical if you have a deep structure with many subfolders.
To work around this annoying issue, I flatten my “giant” folder from my Mac into a single folder. This flattened folder can then be imported in one go on iOS/iPadOS, and relinked into My Collection.
One issue I have now, is that iCloud sync of cue points and auto mix start/stop points etc. does not work. I don’t know if it is related to this way of keeping the DJ library synced across devices.