Whereas your environment reports node v12.3.1, a current ERPNext has this installed
frappe@ubuntu:~/frappe-bench$ node --version
v6.13.1
This list several branches Previous Releases | Node.js
Exactly how to switch node branches you will need to research - you want to preserve and not break your MacOS environment.
edit: netchampfaris advises running node 8.12.0 or greater here Cannot find module 'rollup' - #10 by netchampfaris