Sadly, exFat doesn't work reliably on Windows as I've had random software fail when data is stored on a drive formatted with exFat.

Mostly that's the software's fault, mistakenly assuming anything "not NTFS" is FAT32 and insisting I need to "upgrade" my drives, even though I'm only using it as project storage.

I honestly don't know why user mode software can tell what format the volume is in, and wouldn't just expect the OS to handle it or provide various feature flags like VOLUME_SUPPORT_LARGE_FILES or so.

'Random software' should not know anything about which file system your drive has. If it does (..say.. some kind of whole disk backup utility), and you are using an unexpected file system that is not really a problem in exFat.

The details can easily leak, for instance with FAT in the limited resolution for timestamps or the case (in)sensitivity.

Just a simple counterexample, SQLite is not supported on NFS. Applications are not as insulated from the underlying storage as you suggest.

FAT/exFAT have good support across the three OS's, but they are very far from being "modern" filesystems. One of the most fundamental cons for me is the lack of journaling on these filesystems; it's very easy to corrupt a drive formatted as exFAT, especially if it's a portable device (which is probably one of the most important uses of a cross-platform filesystem)

You can't fix exfat errors on linux (fsck just reports the errors).

exFAT is patented.