If you were a Web developer in 2013, you could find plenty of jobs if you knew Django (Python), Rails (Ruby), Zend, CakePHP, Symfony (PHP), or Spring (Java). Those were the frameworks used by either companies (Zend, Spring, etc.), or loved by devs (especially Rails and Django). Node was starting to come into its own for Web development, but nowhere close to the others.
Fast forward to 2020. Rails and Django are on the decline from their fame peak. Most of those frameworks are still being used for legacy reasons. Web dev work I see is primarily related to Javascript (React, Vue, Typescript) or the JVM (Scala, Kotlin, Java). The other interpreted languages are nowhere close to their 2013 status.
Between 2013 and 2020, we also have a huge ecosystem of Golang and Rust coming out, let alone Docker. All of these helped influence or play a crucial role in developing web sites and applications.
While a lot of these technologies were around in 2013, they definitely weren't as pervasive or mature as now, and developing in 2013 was a whole different animal than doing so in 2020.