No system of government is perfect and without faults. If one is of a negative form of mind then it is not difficult to identify all the warts while ignoring the healthy positives.
From the mid-17th century, for 300 years, Great Britain occupied the Indian subcontinent. During that time the vast country morphed from tribal states to a unified democracy that is now the largest in the world. The Brits left behind a comprehensive railway system, a stable bureaucracy and an international language benefiting world trade. It was only following decolonisation that the subcontinent regressed into partition with three separate states, one of which is in abject poverty.
The former Southern Rhodesia, now Zimbabwe, and Northern Rhodesia, now Zambia, were rich in agriculture with food aplenty for all. They were stable politically and socially. However since the Brits left Zimbabwe the country has regressed. The expropriation of land from white farmers in Zimbabwe has resulted in starvation and inflation to infinity. That is due to decolonisation. However many previously colonised countries have gained much from the legacy of the British Empire that, while being exploitative, was in essence benign and constructive.
Thailand prides itself on never having been colonised. But one cannot avoid pondering whether if it had been colonised, it might now have a comprehensive railway system and an established democracy resulting in political stability. An international language might have made it an exporter of technology, an innovator, rather than an importer of foreign-designed products. It could shake off its feudal past as has India and the education system would be based on thinking and debating rather than the current feudal rote system. As followers of Lord Buddha, Buddhist monks would be teachers, as is their duty, rather than dependents of public goodwill. There could just be greater enlightenment.
Similarly the great coloniser itself, Great Britain, would not be in its current sloppy state of social and political chaos had it stuck to the rules it imposed on its colonies, like discipline, respect, and law and order.