Jess,
There are a load of different needs out there, and loads of tools.
html, js, css are needed to produce pages that function in a web browser (lots of libraries like jscript, angular, bootstrap, lots of examples to copy)
DS is good for writing apps that run on a Android phone/tablet (and Webview can use html, css, js),
and can "talk" to Databases, web servers (JSON); for me the learning curve is much shallower than other IDEs/AJAX/etc
but DS doesn't (yet) support apps on iPhone/iPad.
There is still a place for LAMP (Linux, Apache, MySQL, PHP/Perl/Python) in centralized backend (shared/large volumes of data).
Regards, Alan H