Point 1 is largely true, Microsoft builds too many competing UI toolkits.
Point 3: You can slim down Visual Studio's install a lot if you're more selective during installation. For example if I only wanted to do .Net desktop application development it is closer to 4 GB and under 10 GB on disk.
Point 4: Is actually the end of the original synopsis on the topic and after it veers off. You successfully built the application.
Now it goes a little off the rails:
Point 5: "The app is extremely resource heavy and way too over-featured." Ok? You didn't say which toolkit, guide, or similar you used nor what you define as resource heavy or in what way it was "over-featured." This is too vague to discuss meaningfully (e.g. Win32 applications built in C++ definitely aren't resource heavy or over-featured for example, and since you didn't clarify even what tech stack was used let alone guide/template this isn't constructive at all).
Point 6: I've read this sentence several times but seemingly you opened an executable in a text editor and that somehow broke your build process? Or something? Was it write-locked by the editor?
Point 7-10: You had a working build pipeline, you broke the pipeline, then decided to start again from scratch in an editor that doesn't have native desktop development support on Windows (because the old editor was "bloated"). You found this process problematic.
So in answer to:
> Why is building Windows apps so complicated
You made it complicated by using unsupported workflows and introducing arbitrary limitations on what was a successful outcome. There's a lot you can legitimately criticize Windows and even its desktop application development workflow for, but this isn't that.