As a front-end web developer there are only 2 APIs to learn: DOM and web API (the html5 and browser stuff). Both of those APIs are well documented industry standards. Both change more slowly than the average developer’s career and are almost entirely backwards compatible to their first versions. In short you almost never have to relearn the standards, they always work as designed, and risks of cross-browser failures are largely years in the past.
Yet most front-end developers are scared shitless of writing to the standards directly, because that means writing original code and putting their name on it. Better to play it safe with a giant monster framework and 1000 NPM packages in order to bind some CSS to a piece of dynamic content. The commonality of invented here syndrome suggests that not spending the time to use common libraries is what’s cheating.