Using Linux for years has decreased some of my IT skills! I work in IT, support for schools and small businesses, mostly Windows machines. But in my household and my own office, I've only used Linux for a decade now. Trying to keep a Windows machine around for work stuff. I used to be a badass at Windows support. Doing editing the registry on the fly, solving arcane driver issues, and etc --- but now, I'm not cutting edge on Windows, because I just barely use it anymore! And, I'm not a wizard at complex Linux issues - because I've not HAD to become one. There has been no need for me to become an expert at working under the hood with Linux. It pretty much works flawlessly all time!
Ok, I was just sharing some late night Linux thoughts, its hurt my IT skills because I haven't had to use them!