What would have happened if an otherwise unknown half-crazed peasant from Gentofte in Denmark with a charismatic personality and a mind like an abacus had a most disturbing vision of what it is really all about and launched a new religion that, in a matter of decades, swept across Europe with fire and sword, converting both christians and muslims?
What would have happened if the Chinese peasantry finally had enough, throwing off the yoke of the aristocracy and bureaucracy in favour of a new unique merit-based government based on the skill at playing Go?
What would have happened if the Aztec Triple Alliance had died in its cradle, leaving the tribes to fight eachother and their neighbours rather than unite and fight everybody else they could conveniently reach?
What would have happened if cooler and less greedy heads had prevailed and the thirty years war had been averted, ushering in an age of goodwill towards all (or at least all who were white and christian) in which competition was primarily technological, effectively bypassing the renaissance and punting Europe into the industrial era by 1700 or so?
And as I've said before, plausibility is as plausibility does and there is no way to cover every possibility when making a game.
I quite agree that there are many amazing possibilities in the ROTW. There are many amazing possibilities
everywhere. That's inherent in making a game of alternate history. Thus, what is important when making a game is to know how to
limit yourself and concentrate on making things awesome within the limits you have set, and THEN, if circumstances permit, making things even better outside the limits.
Making games is about constraints and doing the best you can within the constraints. You have constraints of hardware capabilities, team skills, budget, and timeline. You have tradeoffs. Any developer time spent on one attractive task that would make the game better is time that is not spent on another attractive task, that would
also make the game better. So what you do is choose what to focus on to create a killer game concept that you can, hopefully, develop a great game capable of achieving on time, on budget, and on quality.
Paradox has chosen to focus primarily on EUROPE in their Europa Universalis game. To focus on European expansion, interactions, and religion strife. The ROTW is there and is playable, but it is the setting and to a large degree exists as speedbumps for European expansion, not the focus. This is their choice and, given that design choice, it would be the utmost of folly to spend as much effort on the ROTW as they spend on Europe as it would dilute the game as a whole. The EU series has a strong underlying narrative, and a powerful narrative it is: the rise of Europe to dominate the world.
That is not to argue that this design choice is the only way to approach the period, of course; It most certainly isn't, and one can certainly argue that within the scope of the possible it is a narrow focus.
Then again, narrow focuses and clear design goals traditionally make for the best games and are easier to budget for and plan out, so it is an understandable design choice and anybody wanting a wide-open sandbox game that is, as you would have it, "plausible for all countries, not just Europeans", rather than clearly favouring and focusing on a certain part of the world will have to wait for another professional developer to tackle the job and deliver something that does this on time, on budget, and on quality.
(The Civilization series, amusingly enough, probably comes closest to this of all released strategy games, but it is probably not this type of historical gaming you are looking for. But one most admire Sid Meier for the original game concept as it is one of the strongest in gaming even today: Build a civilization to stand the test of time.
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