I'm been a proud vanilla-js programmer for over 2 decades.
The only in-built thing really lacking is customizable dialogs, such as HTML modal and modeless dialogs, and starred password input control dialogs.
All of the typical JS packages are available for vanilla-js, like calendar and color pickers.
What's funny is that other developers' ears usually perk up when you mention being a vanilla-js programmer, and often want a demo to see how you can do entire apps without jquery, etc.