And with n feature flags, aren't there also n! permutations to test, that is, each combination of enabled/disabled? If you say no, because you just test features as they get manually enabled, why can't you do the same by manually selecting branches to be merged?
Yes, that complexity does not go away. But you only need one delivery pipeline, with one test/staging environment. Toggling and running acceptance tests against the variations can be automated, but is viable when done manually.
