I have been using xHTML and CSS since 2002 and HTML5 and CSS3 since 2011. Working for every single telecom company in UK and a few in Europe, I've been developing mobile orientated websites way before CSS3 and media queries were an option.
I have building websites using both vanilla as well JS frameworks since 2002. Apart from the Angular and jQuery I had the chance to work with some interesting frameworks like DataTablesJS, HighChartsJS, ArborJS and Velocity.
As I worked for every single telecom company in UK and a few in Europe, I had the chance to develop mobile/tablet optimized websites way before media queries were an option (back then we used PHP and device detection to output custom CSS on the fly)
I've been using WordPress since version 1.1 and I have been involved in all stages of development, from the custom configurations and multi-site, theme development (for Rolls Royce) and custom plugin development and API integration