The antora UI makes use of the table of content so when a webpage has a large amount of content, it makes it easier for the user to navigate.
I have observed this in Hugo pages such as articles that have a large amount of content as well. So to improve user experience over the Hugo content as well, I suggest adding the toc for the Hugo pages excluding the blog posts.
I have added an image of how it looks. It uses the same CSS as that of antora UI.