Post colonial theory enables to unearth the reasons behind current social reality. Be it democracy, politics, relationship between countries (like commonwealth) etc. Everywhere we can observe the impact of colonial residue. Since, decolonization has remained a 'unfinished agenda' in various aspects. This includes language, ways of knowledge generation, understanding of the reality, definitions of development, socio-economic parameters and such many more. Hence, post colonial theory can definitely be applied to examine such interactions between post colonial states.
I equally agree with Ankur Joshi. Our way of life in post-colonial states always remind us of where we come from. Our frame of reference include this post-colonial element in us. It has shaped even our identities. It has become our history and we cannot shake if off. But we can employ it positively to understand our immediate situations in order to begin to create positive identities that begin to move away from post-colonial thinking to democratic thinking.
Yes, it is fitting and apposite particularly because postcolonial theory though has settled into a pace that has lost the initial euphoria, has settled to a more matured mode. it is highly relevant in the light of emerging realities. it brings fresh understanding to groupings of nations, interests and developments. I however believe a blame all post colonial woes states' on colonialism approach would not really be a development focused or futuristic line of analysis.