Recovering a RAID 0 volume
All consumer file recovery software I've seen and evaluated do exactly what you say. They troll each and every block of the drive and make up stories and file names in the presumption that each block was a file that's now deleted.

Someone has to spend tons of time pouring over each and every file to make sense of them or start looking for metadata (social security numbers, passwords, ascii strings / hex values) and then report how much progress is made finding needles in the haystack.

Normally if you send in drives from a JBOD type RAID to a recovery service - they offer free quotes and can speak much more intelligently about your prospects and if this is a $500 recovery or a $5000 recovery effort.

In your specific case, if the LaCie drive comes RAID 0 by default, there's nothing on the macOS side that made the decision where to store the data - it's all embedded in the firmware shipped by LaCie so your first stop would be to ask them for technical assistance or documentation to see if you can rebuild how they stored the data.

Your diskutil list shows clearly that the drives now aren't seen as a RAID so your diagnosis is correct and you'll want to get software that supports LaCie RAID recovery or hopefully find someone that reverse engineered and documents how to do this. I haven't ever seen such a thing and usually pay if the business need is more than just walking away from the data that wasn't backed up in a way it can be restored easily (or at all).