The truth is spend 10,000 hours building something in a certain language and try to find a job in a related language and those 10,000 hours mean very little.
I strongly disagree with this. I read Teach Yourself Programming in Ten Years for the first time in 2007 and was learning C#. I changed languages 20 times and each one taught me something different or a new way of thinking about an old problem. Those 10,000 hours will be a great investment in your success.