Accidently Erased ./etc/ directory:
Solution 1:
The quickest way to recover from this situation is to restore the system from backups.
The second quickest way is to reinstall it from scratch (don't forget to secure your data, so you don't wipe it accidentally).
Consider using Timeshift in the future. It's a neat tool that lets you rollback the system (not data) to a past version. It needs to be set up before an incident though.