Everything looks simple from the outset until you try to build it yourself.
well that's the trick. If you look at implementing a Web browser or a physics engine you instantly give up, and you are right about it, it's just too hard. If instead you write a partial HTTP client which can display some text from a URL or have a 3D scene and in it an object Y coordinates get smaller each millisecond then suddenly in terms of the essence of each, you are 80% there really. Now if you want to implement the "rest" you might need an entire lifetime, or more. Still IMHO it's definitely worth doing very compact and limited versions of all those in order to learn, even if done only once in your life.
My point is that the essence, the core mechanism, is typically a 1-liner, but only with a pedagogical context, not a production (in the sense of anybody else using it reliably in realistic situations) context.
I also think there is an incredible transference of skills from one domain to another. This is a risk (everything looks like nail when you have hammer), but there are many domains that are very mature where you can learn a trick and apply it to a new domain over and over again.
but unfortunately not everyone have same opprtunities
Besides, statements such as "$7B for a proxy" or "it is just a wrapper" or "we can build it in-house" mostly come from those that have not had any measure of the scope due to not having any real experience with the said problem.