I was one of the first posters on this thread, and I am very happy to report that, after updating my IOS (IPhone 8) to 11.4 today, and updating ITunes to version 12.7.5.9 (released today), syncing my 4800 photos locally (not ICloud) through ITunes took just over 5 SECONDS. I have synced three times, just to verify, and subsequent syncs were essentially instantaneous.
I made NO other changes to my Windows 10 system, except to install these two updates from Apple. I am going to pronounce the issue resolved, at least for me.
Looks like Apple was listening after all. I just wish the tech support people knew more about what was going on in development. My experience with Apple Customer support throughout this process was essentially useless, right up to them replacing my PHONE for what was ultimately what we all knew.....a software bug in either IOS or ITunes.