I've been to IO Interactive and seen this game be developed.
It's truly amazing.
Here's a picture.
https://i.imgur.com/cK3WeYo_d.webp?maxwidth=640&shape=thumb&fidelity=high
https://m.imgur.com/t/awesome/jwwPgRg
Tbh I'd way more like to play on a cross platform app instead of on a browser. Most likely the app will be written in Electron (node.js) and their client in html5 since their web app already uses a rest api and Angulat or maybe Java.
Tbh I'd just recommend NOT to use anything related to RevCMS as it's both deprecated and outdated.
Even back when it was first created it was using bad practices.
To be fair, @Kryptos probably wrote the original release within a few days.
If you look at the threads there's actually plenty of good developments that are active, it's just most of the users on here that aren't willing to support even if it's Habbo related.
JS (I think) is also the only language to support all platforms aswell as React as a library without having to use different languages/libraries for each platform.
I'd say JS is the superior language for mobile and app development.