If that is true, then why shouldn’t someone use GWT and use Java on both the client and server? Since the JVM works very well on the server, certainly the effor

If that is true, then why shouldn’t someone use GWT and use Java on both the client and server? Since the JVM works very well on the server, certainly the effort put into GWT could be seen as the equivalent of the effort put into Node.js to make a browser technology work well on the server. At the least, when you hear the “same language” justification, you should be looking for places where the same justification could be made but you don’t find it convincing. If the justification isn’t convincing when you substitute analogous elements, then either the justification is flawed or it is missing something that would differentiate the two situations. In my opinion one of those reasons would be that GWT is written in one languadge and translated into another, where Node and the client side use the same base languadge. I do not see it as an apples to apples comparison.