For me, the GUI is a secondary reason for using Strapi.
My primary reason for using it is this: it imposes a little bit of structure and opinion on your node app. Just enough so that your project isn't a mess and you know where to look for things, but not so much that it restricts what you can do with it. Basically, it bootstraps Koa and Mongoose (and some other tools) in a really nice way, and gives you a nice way to configure/use them. After building Express apps, it was refreshing to have some structure and eliminate some of the tedium of setting up projects.
Although I'm not using the GUI for adding content, I have found it very useful during development (inspecting data and relationships), and can help in tracking down issues in production. With Strapi's GUI, if pieces of data are related, you can easily jump between them - as far as I know, this isn't something that can be done in a MongoDB client (like Robo3T).
If you've ever built an app with Express and Mongoose, I recommend at least trying Strapi. I was skeptical about the "headless CMS" nature of Strapi at first, but that's just "icing on the cake" for me now. Don't think of it as something like WordPress - think of it as a structured Node app with a convenient GUI placed on top.
Thank you very much for the detailed explanation. I will definitely take a closer look at Strapi.
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