The hosting/CDN requirements of the platforms you mentioned, (so that a site can load within an acceptable time frame) as well as the constant security updates are not for me.
Hugo is super fast in generating a site. And a static site can be hosted anywhere without a lot of costs and load at an acceptable speed.
Also Hugo is very simple (once one grasps its concepts) and the customization options are endless without having to use too many scripts or hacks (if any at all), unlike the aforementioned platforms that are very opinionated.
Now about my need for a CMS/GUI for Hugo...
Handling that many images is a bit cumbersome with just a text editor -even an amazing one like Sublime Text-.
I need a way to preview the images while I type captions in a WYSIWYG editor.
Sure I can have Hugo Server running in parallel while I edit in Sublime Text -that's what I am doing right now- but still it's not that convenient switching windows all the time.
So that's why I'm looking for a GUI for Hugo or even a Markdown WYSIWYG editor that can accept Hugo shortcodes while giving an image preview (there is none that I know of).
And there are some good frontends for Hugo and other static site generators out there, (the term is Headless CMS) BUT these are hosted solutions and they cost something around $120 per year.
Also I have found out the hard way to never (EVER) trust hosted solutions again.
Anyway I'm still looking at my options and what I can do with existing tools.
A few hours ago I discovered the amazing Dropbox Paper Editor and I'm already thinking of ways I could implement it in my workflow.