Comment by tracker1

There's JS tooling for bundling so the code over the wire will only include the files and modules referenced.

Much like a function in a C source for doesn't output two files, the bundled and monitored output is only one file much of the time. The browser doesn't download 1400 separate files or even all the code in those dependencies.

For React in particular there are development and production versions of the library.

Not that bundles can't or don't get huge. Not that they aren't often excessive. Only in that they aren't nearly as bad at first glance.