If you install wordpress, and then grab a bunch of plugins and themes and install them without taking any care, it won't bundle and minify your javascript. It's no different to having a static website and grabbing a load of jquery plugins and throwing them onto a page.

But if you use some techniques such as building your theme and plugins using gulp or similar, you can have your wordpress site outputting bundled and minified javascript.

There are also caching techniques that can be used at the webserver level, just like any other website.