I will be honest here - this feels like a further shift from a more simple, straight-forward approach to a more programmatic approach. While it obviously opens up new possibilities for site creators, it also introduces extra complexity.
As someone who no longer codes for a living, my first reaction is to start Googling for Hugo alternatives. My sites are all personal and I want to keep them simple. Using a single binary file for Hugo was simple. Installing and learning Go is not.
Hugo Modules is an optional feature. If you like your site workflow as is, keep it that way.
Yeah, I think a key distinction is that Hugo (like many static site gens) sit at the intersection of User(content editor) and Developer – often because they are one-and-the-same, though not always.
Hugo Mods def falls in the “Developer” set of features (as does custom themes/layouts, templating, etc.) Even within the “developer” set of features there is a natural gradient of complexity which only needs to be descended if one wishes.