We are digital librarians. Among us are represented the various reasons to keep data -- legal requirements, competitive requirements, uncertainty of permanence of cloud services, distaste for transmitting your data externally (e.g. government or corporate espionage), cultural and familial archivists, internet collapse preppers, and people who do it themselves so they're sure it's done right. Everyone has their reasons for curating the data they have decided to keep (either forever or For A Damn Long Time (tm) ). Along the way we have sought out like-minded individuals to exchange strategies, war stories, and cautionary tales of failures.
exFAT solves the cross compatibility issue by removing most features other modern file system have. Fine for some users but not necessarily something I would recommend to someone with a drive array.
On top of that those USB RAID enclosures kinda suck. Unreliable, minimal status info and rebuilds tend to be tricky at best. You should not use them unless you are forced to.
A NAS is likely a much better option and they do not cost that much extra compared to a ~4bay RAID DAS.
Agree with the NAS suggestion. Will be more convenient and reliable than a USB RAID enclosure. I would look into Synology if you want a ready solution.