This position paper provides first, a literature survey of selected domains with significant contributions to simulation interoperability research, such as defense and healthcare simulation, including insights from academia and research organizations. Next, four main interoperability methods are reviewed, i.e., messages-oriented methods, use of information exchange models and common object models, and reference modeling, including ontological means. This review leads to the observation that successful approaches do not only rely on technical solutions but are also using conceptual alignment of the underlying models as well. The Levels of Conceptual Interoperability Model is revisited to consider how it contributed—and still contributes today—to reach meaningful interoperability between model-based solutions. Its descriptive and prescriptive use is discussed, and it is applied to the four methods to show its practical applicability.