Everything changes in tech by the minute ... but also nothing changes. For web applications it has been HTML, CSS and JS for nearly 30 years. XMLHttpRequest/AJAX came out 25+ years ago. There have been many improvements along the way, like applying design patterns instead of cgi-bin directories with scripts that had a +x modifier on them in the file system. But the base technologies have not changed all that much. We still submit HTML form's with input fields to a back-end server that handles that data. We're still rendering HTML and using CSS to style it. Gone are custom UI toolkits like Flash or Java Applets. Maybe WASM is something to look into but it feels like its not mainstream to me.
If you don't want to get left behind, learn the basic building blocks at a deep level, they don't change much.