It's not meant to be a replacement for CLI. I can imagine lots of use cases, even for me. Example: I used something to bulk convert images (resize, crop, convert from one format to another). I used it maybe three times in my life, every single time I had to read the manual. If there was a simple GUI, I'd save time.

My main project is a mobile app that has a bunch of calculators dedicated to specific tasks. Some of this tasks are less-than-trivial, but most of them you'd not look a special tool for (for example VAT calculator). It has 950k downloads, most of its users are very happy with it. But every single time there's a review in the online press I get "this is for morons" comments. Every. Single. Time (unless it's a small blog that doesn't have commenters). When I saw Gooey, I had two thoughts: "Nice" and "Someone will surely try to make a point that this is stupid".