5 years ago PC phones coy decided on W3C format use html5 CSS and JS to clean up the mess.
Just imagine coders hv to learn so many codings to design a UI. Google uses Java, Apple uses Objective C++, and raspberry pie codings uses by Jap.
Coders or developers decide what they find quick and easy to codes in mobile phones and bang use JS. Btw, change in mobile phone UI uses SPA (Single Page Application) just simply scroll in one page (document). The PC webpage is hard to view in small screen phone so change to passive viewing is needed.
This screwed up coding big time and W3C standard was adopted.
From there onwards is all JS coding.
What you see demand for React or Angular4 coders are simply offshoot of JS.
Just need to learn JS well the React (created by Facebook) is just simply add the keyword React.object.value in front of the basic JS.
AngularJS1 was created by Google was a mess and AngularJS2 fixed up the mess. Angular4 Will get into a mess soon.
There are NodeJS, commonJS, VueJS, and more are just kaykiang coders want try something new but will never make it.
Wait till you get An neh versions will screw up big time.
There is one new JS that write into the server side. No need downloaded JS into yr mobile phone.
See simi lanjiao Americans come up with unsustainable programs better China invade US with nuke and leave that land toxic for 500 years to clean up angmoh mess.
If you graduate from university and found a job flipping burgers at McDonald’s you too would think that a university education is useless. The point is that if you are in a job that “demands proficiency in ReactNative, Angular, Tomcat, MongoDB etc,” you are the equivalent of a burger flipper in the tech industry. If you had played it well you would be managing people who manage people who are proficient in ReactNative, Angular, Tomcat, MongoDB etc. Don’t blame your personal failure on university education.