In general, without the Second World War, we see decolonialization taking longer, the colonial powers being more reluctant to abandon the system and less clear pressures for them to do so. I think any colony will reflect the culture of its colonizer, so the British and Dutch influence will be towards democracy under a monarcial mask, generally liberal and capitalistic. These will foster a local middle class, a local government and economy like that in London or Amsterdam, those also will be the people torn between loyalty to the system and pressing for more autonomy. I except the Belgians because they, despite being another relatively liberal European state, behave as ambiguously as do the French, more neglectful, less investing and ultimately more ineffectual as colonial powers. I think their history in the Congo spells out just how hopelessly unconcerned they were for anything beyond exploiting what they could. All colonies featured some exploitation, but in return there was investment, there was education, technology transfer, development, often more so where the colony offered a good return on investing rather than merely stealing. WW2 brought the anti-colonial forces to the fore, both the USSR and USA had motivation to unravel the closed markets, bottled up peoples and web of relationships that did not flow influence or wealth back to them. I think we underestimate how much those two powers undercut the colonial system. This merely fanned the flames of what Japan began as it tore away the veneer of European power and superiority, the Masters had lost the loyalty, respect or fear, and felt the potential for independence.
Generally I feel the colonial system would have endured, there would be independence movements, there would be revolutions, slowly pieces of Empires would be left on their own, but the valuable or prestigious pieces would be kept. Without the war and the following Cold War, there is more will and more wealth to stay at the counter-insurgency game, this is a world of more brush fire wars, more Vietnam style morasses, a bloodier transition for some, yet for others a soft fall to autonomy and paternalistic vestiges of Empire. The Dutch Indies likely sees some insurgency but otherwise I would predict it gets stamped out enough to have the Indies settle into a benign relationship to Holland, exporting oil, reaping some of that back, gaining development and looking more Dutch. The Congo will look much as it did, exploited, violently rebelling, violently suppressed, the Belgians lose the will, freedom comes in a spasm, power grabbed by local strongmen, they have legitimacy for waging war on the foreign masters and see little else but keeping power through that armed resistance to everything opposing them. Without outside influences this may take another generation, or two.
In my opinion the end of the colonial system is neither boon or bust, messier or better "organized", it is varied process with disparate outcomes for every people touched by it. Much of the former Empires echo the cultures, languages and patterns of their past, some have blossomed, many have wilted, simply removing or retaining the home power does not clearly improve or destroy these places, their legacies and futures I feel are more complex than when the last European sets sail home.