In recent years, so-called coproductive, radical strategic planning has become a synonym for integrative and holistic public sector-led planning processes and the alleged integrating qualities of representative democracies. However, these views remain framed by the specific discourses, perspectives and path dependencies of governments, obstructing opportunities for radical reorientations as intended above. In this paper, we want to illustrate how these restrained views affect concrete planning practices through the specific case of the region of Flanders (Belgium). For decades, the holistic model of the Dutch neighbours has largely inspired planning dynamics in Flanders (Belgium). As such, in 1997, most concerned Flemish authorities accepted the first overarching spatial policy plan for the region. Fifteen years later, however, original commitments have eroded and the original plan has largely lost its credibility. In 2011 a new process was launched, aiming to develop a new policy plan (the future Spatial Policy Plan for Flanders). However, this new process builds only limited support and credibility outside the select group of involved actors. We argue that today in Flanders the borrowed methodology of coproductive planning is insufficiently adapted to the institutional context and is therefore mainly delivering an aura of sustainability optimism to on-going policies, while a variety of spatial developments that are recognized as fundamental or problematic are omitted from the debate. We show this by putting forward some major missing pieces, which are located in the policy fields of large road infrastructure development, “legacy” suburbanization, retail siting, and property taxation. We show that these issues are representative of a number of constraints that are imposed by separate policy levels (located at other ministries, at the federal level, or in neighbouring regions such as Brussels) although these are not accounted for by the current planning process, apart from a number of key issues that are kept ...