idk, feature flags for the entire application seem ok to me. The issue is when we want to add feature flags for part of the users, or only on a part of the application flow. Then it will become a mess.

Where I work, those feature flags are used to deploy a feature for a single application "run time", i.e. a country, which has its own cloud and everything.

BTW have you read the article on feature flags on Fowler's website? Could help you form some opinions https://martinfowler.com/articles/feature-toggles.html