This question is very simple : Should we introduce a code-golf where only popular/unpopular programming languages are allowed ? And if yes, how can we measure popularity ? Probably with the Top of the TIOBE index ?
Have you seen the list you have linked to? The top twenty languages go from well-used but not golfing languages such as Java and C to other languages not used on this site. Number 20 is Scratch, for God's sake!
What you've just said, correct me if I'm wrong, is that you want to allow people to compete using Scratch, Delphi and MATLAB but not Jelly, Pyth and Cjam? These last three languages are so well-used that there was even a suggestion (albeit not serious) to change our name to acknowledge this.
This just sounds like a bad idea both for the reason above but also, as @DestructibleLemon1 said, you'd be excluding most programming languages and every golfing language.
1: Just wanted to expand on why this would be a bad idea