People use “serious” to mean very different things: exclusivity, cohabitation, marriage, children, companionship, or simply no casual arrangements. Ask for the definition.
What matters in practice
Marriage-minded dating is not a demand for immediate commitment. It is an agreement not to conceal the destination while evaluating the journey.
Profiles work better when they name the future positively: what kind of home, partnership, family, faith, or community someone hopes to build.