All of these companies have one thing in common: They hit limitations of these frameworks (e.g. Angular 1.x), but they already invested lots of resources in it, so they and the community make sure to introduce solutions for these issues (e.g. Angular 2). With growing applications, it's not as easy anymore to migrate from one to another framework. Most of the companies make it work with the one framework they have chosen to accomplish their mission. Double down on one as they are doing it.
If you want to learn backend development with Node.js, double down on one framework which enables you to create client-server applications. How things get implemented doesn't change a lot jumping from one to another framework, if you were able to grasp the concepts behind routing and middleware. Express, Koa, and Hapi just become tools with different implementation details.
The future of web application will move towards serverless anyway. You will not need to set up an entire server application yourself anymore, but still be responsible for your API. However, I feel at the moment it's the perfect time to still learn how everything works in basic Node.js for client-server architectures, by setting up a backend server yourself, before everything moves into "serverless" functions.
webpack, alt: parcel, no gulp or grunt anymore
mostly you will not see anything of it, because it's abstracted away
one package manager npm, there used to be more (e.g. Bower)
IDE integrations are becoming popuklar right now. Not so long ago, people used barebones editors
- Css (flex box, grid, just apply some margins and padding’s, borders and you are good (see this simple GraphQL react app)
- CSS in JS
- maybe sass, CSS modules, less not as popular anymore
- Deno, Web Assembly, JAMstack, Serverless, TypeScript, GraphQL, learning the previous things first should give you the best fundamentals to look towards the shiny new things in the future (or hackernews).