Obviously, a lot of companies still have plenty of all Vanilla JS projects, jQuery, etc but it feels from jobs that recruiters send me (and companies whom I spoke with) that almost all new development is using React.
For my background I’ve been developing with JavaScript since 1998 and have developed applications and sites with a wide range of popular libraries over the years so I’m comfortable with Vanilla JS. React, and more. My preference is actually Vanilla JS (even using Web Components) over React but it feels almost unheard of in the current environment.
At my current job I pretty much use everything (React, Vue, Vanilla JS) and even maintain some very old Classic ASP sites. For a new project I’m starting (everything from scratch – database, back-end, front-end) I’m currently debating whether to use React or Web Components.
There are some exceptions — e.g. Pieter Levels (RemoteOk, NomadList) who sticks to Vanilla for everything. But it's rather rare.