I don't agree 1:1 with @rajkumarpb, but thinking an OS is holding you back ?? I don't think that's probable unless you use OS/2 or dos + novel netware, that shit is old, get out of the 90s :D
And yes companies do care about the technology, but I got hired for java because they needed some one who knows about cpu-architecture + memory + streaming + network + virtualisation because it was more important to them I understand the system than the language. And I only wrote java 3 times in my life helping my girlfriend and ofc I told them upfront.
Understanding how technology works trumps understanding a specific implementation in general you always have an introduction period and I personally try to get starters from the universities so they can learn .... so I wouldn't worry to much about the operating system and more about the idiots who tell you what you can or cannot do :)
Opinions are like assholes .... everyone got one ! :)