Unable to get the FieldInfo's value

public static List<T> FindInstances<T>(object value)
{
    List<T> instances = new();

    Type type = value.GetType();

    foreach (FieldInfo field in type.GetFields())
    {
        if (typeof(T).IsAssignableFrom(field.FieldType))
        {
            object fieldValue = field.GetValue(value);

            if (fieldValue is T instance)
            {
                instances.Add(instance);
            }
        }
    }

    return instances;
}

public string string1 = "string 1";
public string string2 = "string 2";