I found the recent Abseil article Performance Tip of the Week #52: Configuration knobs considered harmful to be insightful. Most people, developers included, would generally prefer more flexibility and configurability over less, but as the article points out, configuration options (flags) carry risks and complexities that are not evident.
Part of the problem is that configuration options often can only be set by the authors correctly, because they are the ones who understand all of the necessary context and who are aware of the subtle details. More configuration choices also increases the complexity of the application, making it more difficult to maintain and improve. Furthermore, as software evolves, configurations that were desirable in the past might become undesirable (e.g. due to some optimization becoming a reality) without anyone noticing.