I had this issue as well. If you verify the Rocksmith files on Steam, it fixed the crashing issue for me.
Steam Library > right click Rocksmith 2014 > Properties > Local files > Verify integrity of game files
This allowed the game to open properly for me. Now I've gotten as far as choosing a CDLC, tuning, then it pauses indefinitely because they haven't patched it yet for the new Mac chipset on Monterey. Praying for a hero to patch this for us folks with the new computers.
Also, a note on the 'unidentified developer' topic, they explain how to get around that at the bottom of the page for the 'CDLC how-to' on Mac.