If you run a repo-only system, where everything you install comes from the first-party distro repo, you'll likely be fine. Just as you are on Windows or Android if you only download apps from the first-party store.
But like on Windows and Android, you'll quickly reach the limit of what you can do with first-party store only.
Especially stuff like gaming requires non-repo/non-store stuff pretty quickly, and then you are on exactly the same turf as on Windows.