If you can wrap your head around advanced C++ concepts and idioms, learning other languages will be a walk in the park. All the knowledge will be 100% transferable to anything you use in future. Also a lot of companies using java, c# etc will take c++ experience as relevant experience even though you aren't a java/c# expert, but the inverse is not true.
It's never a bad idea to learn something that has shaped essentially everything that has come along since.
I have that book and it is a fantastic reference, but it is not great at instructing. There are no comprehensive examples so it is hard to see how all the parts fit together as in best practices.
First off, insulin is HARD TO MAKE. Its synthesized rDNA, this isn't the same as making pills out of powder from china and selling it at a 40% discount with plenty of margin still. This has to be grown and made in a lab with a very high precision.
Second off a bottle of insulin is like 25 bucks..... Boo freaking hoo. Most people cant wrap their head around how insane that is. You are buying f*ing DNA.. that someone made.. that's saving your life.. for 25 bucks.
What was the purpose of bell labs making unix or linus torvalds linux? Why is apache free? open source C compilers? python, java, mysql, go-lang, rust, angular the list goes on.
Open technology helps evolve the type of applications we can build. There doesn't have to be a "play". Facebook made something good that makes their lives easier and their product better. By open sourcing or sharing react whichever it is they allow other people to contribute which in part makes their product better but also increases the quality or reduces development time of the applications that anyone else using it builds.
