We're not quite there yet.
Apple says that High Sierra will be the last version of macOS to support 32-bit apps “without compromise.”
The timeline is...starting in January of 2018, all new apps submitted to the Mac App Store must be 64-bit, and all apps and app updates submitted must be 64-bit by June 2018. With the
next version of macOS (after High Sierra) Apple will begin "aggressively"
warning users about 32-bit apps before eventually phasing them out all together.
So we've got a little while yet (around 2019) and as I understand it, from postings here, Photo Mechanic 6 is currently feature locked so I assume it should be released before the next version of macOS (I hope!).
Looking through my list of 32bit apps, the vast majority are from Adobe.
As I understand it the current situation is..."Don't Panic!".