I agree, but only until the part you mention how people should install their software. And that's simply because I don't think that people should install random .exes or .debs from the internet, because repositories are:
- Easier to find software within: you've got a one-stop-shop for all/most of your most important software
- They're inherently more secure as the software should (emphasis on should) be checked by maintainers or the people who upload software onto them
- Software updates are much easier to enroll, as they are treated as system updates