While I respect that this approach might be working for you and your team, I'm going to strongly disagree here.
Any developer that has work on larger projects, and with a fairly large team will be able to tell you that following your approach is more likely to cause lots of merge conflicts, making the code harder to audit, and slowing down the team.
Not all features are so trivial that can be wrapped in a feature flag while they are worked on, and that is not to mention that you are increasing the cyclomatic complexity of your code with each flag added.
In my experience, short leaved branches (GitFlow), Code Reviews and proper CI/CD tools take care of most if not all issues you can have with topic branches.
Finally, I would urge people to be more careful when expressing "controversial" opinions like this in such a matter of fact on a website that has a great number of developers starting or looking to start their career
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