I guess I'd have to say that WordPress, Since 2003 has taught me, or lead me to learn..

1. Direct Custom Programming within WordPress to remove the Performance Bottlenecks.
2. Advanced NGINX Developement, I have my own custom nginx server which directly supports WordPress in many ways.
3. Advanced Ubuntu Development, I now custom build and Configure Ubuntu for Speed, using only the advanced software needed to run Ultra-Fast Wordpress Websites..
4. http://boi-infinity.com My wife and I run a high traffic WordPress + Woocommerce Website for our Private Server. I'm also an MMORPG Programmer but the site has taught me a lot about website security and other issues that most other WordPress websites would never face.. We get 1000+ hack and security vulnerability attempts each day!

Thats what I'm thankful for..
Chris