jQuery can still thrive in the frontend world. It can live happily between vanilla JS and the modern big moderns JS frameworks. Not every developer needs to use a Single Page Application (SPA) framework and many developers use a SPA when it’s not needed. They only use one because it’s the hot thing to do and their site is a simple site that doesn’t require any SPA.
While modern browsers now support what jQuery was known for like its flexible selectors, it still has some very useful utility functions and uses. It’s plugins market is also huge. Even some commercial UI components use jQuery in them.