"If intelligence-driven extinction doesn't explain this great cosmic silence, then what does? Why hasn't our species heard from other intelligent civilizations elsewhere in the universe?"
Maybe time. In the scale of the universe's existence, we have been aware and looking for intelligent civilizations for a very brief span of time. Also, what we would be able to recognize as intelligent civilizations may not even be recognizable for us or for said civilization.
My list goes like this:
- Telecom
- Information Security
- Human resources
- Systems administrator
- Network administrator
- Network cabling
- Database administrator
- Systems analyst
- Windows developer
- Android developer
- Apple developer
- Web developer
- Helpdesk for in-house developed programs and everything else
- Graphics designer
- In-site hardware maintenance and repair (PCs, tablets, phones, scanners and printers/mfp)
- CCTV installer/administrator
- RFID antennas install/configure
- Telephone and cellphone plans management
- New hardware and software technologies investigation
- Social media manager
- Scale calibrator
- Microwave configuration
- Professional spider killer
- Landscaper
- Charisma and good vibes enabler
- Sex-ed