@Nostalgium This is the first fair counter-argument in the thread, so I'll endeavour to respond bit by bit.
People complain about that, too - especially Persia and Muscovy, because they're important counterbalances to the Ottomans.
What does it say about the Ottomans eventual power that the main point in the development of other countries is if they can withstand the Ottomans or not?
The fact is that even if we had a united Persia they'd get steamrolled by the Ottomans on pure quantity. The Ottomans also have the benefit of having the entire Levantine culture group as their home culture, which is inaccurate, meaning they have insane benefits from the land they conquer. Relative to the Ottomans, Persian lands are poor.
In the case of Muscovy/Russia, they're only on Ottoman level after forming Russia, colonising Siberia and sorting out their economy. The Ottomans again are far richer than Russia ever will be. This may be a fair point of gameplay but I feel compelled to point this all out.
France and Britain more seldomly, because France is usually in the historical region of powerful anyway and Britain is crazy strong in the least fun part of military gameplay, but y'know. Another common complaint is Mughals hugboxing itself in in India and becoming a steppe empire instead, if they form at all.
The development of France is very RNG. The strength of the HRE, the outcome of the Burgundian Inheritance, and whether England/Castile form an early alliance can have existential differences to France. I don't think the Ottomans have anywhere near the level of RNG to deal with, even in the case of the AI. British AI still doesn't know how to deal with naval landings either.
Their military ideas aren't as OP as people seem to think, and the bulk of their strength comes from enormous manpower, which any quantity-focused country conquering the region will also achieve.
A couple of things to point out.
EU4 is largely a quantity based game for AI battles. The Ottomans reach an unstoppable level of forcelimit and manpower long before anyone else can contest. (and realistically who will contest them other than Russia?) Therefore the Ottomans are able to defeat some of their potential rivals very early on in the game. This is made worse by their siege ability age bonus. It's also why them taking Quantity ideas is just vile. It's a guaranteed game over for any AI they fight.
In the first 100 years they are ahead on pips, tech, manpower, forcelimit, siege bonus and income than any of their potential rivals and by some margin. It's not unfeasible for Austria-Hungary-Venice-PLC-Mamluks and even Muscovy to all be defeated by the Ottomans within the first 80-100 years of the game. At that point who is going to stop them? The game offers zero mechanic. You just don't see large empires crumble in this game (this isn't an Ottoman specific issue).
They're strong more out of circumstance than anything more easily nerfable, and creating a situation where they're not a two-million manpower monster relies more on strengthening their neighbours by encouraging consolidation, but this is hard to do through AI improvements (from which the Ottomans will also benefit) AND strengthening tags, with for example PLC and RUS as that will affect other tags before the Ottomans.
I and others have said they just need a disaster or two.
They're the only major tag I can think of that doesn't have to deal with a major disaster. The Janissary coup realistically never happens. Meanwhile the War of the Roses drains English manpower/finances for over a decade. The French Wars of Religion gives me Vietnam flashbacks just imagining dealing with it.
The Ottomans should get a malus to embracing Institutions Printing Press and beyond. And they should have events that give very high autonomy or unrest in the Balkans.
I also think the +33% siege ability should go and be replaced with a manpower related bonus.
They shouldn't be in the Levantine culture group either. Turkish should be in its own culture group.
Finally, the awful, a historical Crimean event needs to go. It messes with the PLC and Muscovy far too much. The Ottomans don't need free land. Give them perma-claims on Crimea and the Black Sea whilst you're at it.
I am absolutely certain that these things above would create a more balanced game in which the Ottomans are still strong, the Ottomans still have the potential to be the world power, but there's enough variables for it to not happen every single game...