The original question was never answered - How to import a Playlist? If it cannot be done, please say so. Having to rebuild the house since one brick is missing seems an unduly onerous way of solving a problem
The way you described in your original post.
Unfortunately, it seems that importing playlist using CSV files isn't working at the moment. If you had exported those playlists in MPL format then the import would have worked.
When you buy a new MacBook, there is a "Migration Wizard" which transfers all your existing information and settings to the new computer so you can start off from the same place you left off.
It's not really fair to compare JRiver to Apple. Think of the difference in revenue and user base!
But MC also does this, when you use the Library Backup and Restore functions correctly.
Did you Google how to rename a drive in OSX? There is heaps of information on how to do it, and the exceptions. Read BOTH of these links.
https://forums.macrumors.com/threads/renaming-the-hard-drive.1295428/https://kb.iu.edu/d/abtqWhat you should have done, and should do now, is;
Shut down MC.
Rename the replacement drive to the same name as the old drive, as per links above. The name of your old drive will be listed in the MC library as part of the file path.
Restart MC and make sure it doesn't try to start importing anything. It probably won't, since I assume that MC is installed on another disk, and still works fine, but is just pointing to the wrong spot.
Restore a Library Backup from before the HDD crash.
Then you will have your library back intact, with all playlists, as long as there aren't any other issues you haven't mentioned.
PS: "Find & Replace" is part of the "Rename, Move, and Copy files" function inside MC. it is at the bottom of the dialogue. If you can't rename the disk even with the above advice, you should still restore a backup and then use "Find & Replace" to change all references in your library from the old disk name to the new disk name.
If you get stuck on that, search the Wiki for the "Rename, Move, and Copy files" function, and search the Forum for descriptions (Brian's are good) of how to use the "Rename, Move, and Copy files" function "Find & Replace" to fix issues like this.