Learning a new language to improve your programming skills is truly a cliché. Instead the proper advice should be "I should learn a new programming language so

Learning a new language to improve your programming skills is truly a cliché. Instead the proper advice should be "I should learn a new programming language so I can escape my myopic understanding of the practice programming." Building applications, as you say, is of course very instructive, but tackling a language which has very little relation to the ones with which you are familiar has benefits which are pointless to reduce to "it will make you a better programmer".