It's not a simple gamestyle choice as you put it. If world conquest is possible it is because the game is dumb down and easy enough that those who just want to get a realistic size empire, just get bored because it is too easy to achieve. And it is made easy to achieve because a world conquest needs to be possible.
The result? The EU4 problem where people stop playing the game, and those who do play it drop it in 1600 because the game is to easy and the only thing left for you to do is to conquer the world, which is not a challenge, just a tedious chore. And forcing the player to drop the game because it is boring and it has already achieved by 1600 empires that realisticalyl should only exist in 1800 means that the player misses on 200 years worth of content. That means that the time of the developers goes to the bin, is not monetised, and is a loss for Paradox. The result? The developers just add content up to 1600 and design the game with 1600 as the effecting end date.
This is completely backwards and ruins the game and renders 200 years of the game available just useless and you might as well have the game end in 1600. If your end game in 1821 or whatever, you have an obligation to make it enjoyable and have content until the very end date and keep it challenging up to the last date so people who have paid for the whole game, enjoy the whole game, from day one till end date.
If you just want to see the whole world of a single colour and care for nothing else, keep playing EU4 or just colour a map on Paint or something, but do not ruin the game for the rest of us or deprive us of 200 SUPER interesting years of history with amazing content like wars of religion, the expansion of the British empire, the American and French revolution and the Napoleonic wars.