Constructivism is in some ways more challenging that traditional IR theory. This is because there is a spectrum of difference between constructivists.
In the case of classical v structural realists and liberalism v neoliberalism, a large part of the difference has been time. These are theories that have evolved to keep pace with new world events and new global understandings.
However conventional constructivists and critical constructivists are not evolutions, they arose within a similar time period. Although they are grouped together because of some shared foundations, there are huge differences between them.
Due to this, constructivism can be considered a 'middle ground' between critical theory and traditional theory. Although this is debated. If you would like to read more about constructivism, please connect with me.