Welcome to the business, for better or worse. Technology stacks have a pretty short shelf-life with very few exceptions. I've been in the business 20+ years, most of it in Silicon Valley, and with few exceptions, like Java, most development platforms do not last even five years. It is one of the reasons I have experience with so much obscure stuff. I am constantly moving through technology stacks.

You might not like it but you need to follow the tool chains. Specific to your situation, I do not know anyone doing Ruby anymore for new systems. I am sure some people are but it is clearly on the decline. Continuous evolution of the tool chain is the curse of our industry. Right now, Javascript is probably much more valuable than Ruby.

If you do not like trading up, some skills are more durable than others. Over the long term, I've seen C/C++, Python, and Java retain their value better than most languages over the years. I think Javascript is likely to add itself to that list.

While you might find it depressing, a lot of what you have learned is immediately applicable in these other environments. You just need to figure out how they map, which is not too difficult. Going from Ruby to Python or Javascript is not that big of a stretch. In most cases, it is a weekend learning syntax and tool chain differences.