My problems with the changes in 1.26-1.28 in a nutshell: Strong things got buffed, weak things got nerfed.
Worst offender: Trade Companies. In 1.25, the best move is almost always to get some of them as your economic power base - be it by going towards India as a European or African or by moving your cap out of Asia if you start there. 1.26 then introduced penalties that are more or less countered by TCs.
Convertion is considerably slower now? Just conquer TC land, you don't need to convert it since both negative Tolerance and Religious Unity impact are ignored. And after a temporary pullback in 1.27, 1.28 pushed further into 1.26's direction by making convertion even slower (through the effective removal of your vassals' missionaries), more expensive, and more annoying (since you can't increase autonomy anymore and half-stating is more or less obligatory in the early- to midgame).
You want to conquer the piss-poor steppe lands in order to make you name nice and big, but you can't afford to pay down the ensuing corruption? Conquer India!
You're approaching your state limit, so you're worried that future conquests will have massively reduced pay-off? Nah, just conquer India!
The Ottomans are once again crushing it and you just can't keep up with their income and forcelimit? You guessed it: Conquer India!
You're going for the African Power achievement? First of all (well, after unifying your home region), you should snipe the cape from the Europeans, monopolize Zanzibar and... Conquer! God! Damn! India!
I'm sorry, but I just cannot see how it is more engaging or demands more thought from the player when the answer to 95% of the questions that EU4 poses is "go for TC land" (the remaining 5% are solved by no-CBing into Ireland). To quote the
Dharma manual (which I think I've done before, but it's too good to pass up):
By setting up a trade company in foreign lands, colonial nations are already giving up a few other things. Trade company provinces do not provide manpower, and cannot be a part of States. Therefore the economic benefit of expanding your trade company beyond a rich city may not be enough to persuade the cautious player to take the risk for ready cash.
In the current state of the game, this is pure mockery - even ignoring the factually wrong (TC provinces do, in fact, provide manpower) and misleading (TC land not counting as states is a big
advantage) parts - but I'd be very happy if the devs would come up with a rework of the whole system that makes it an actual decision whether or not to press the TC button, be it by resticting the amount of TC land one can have, by heavily nerfing Trade Companies, or (preferably) both.
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And honestly, the way Humanist was nerfed also fits in the nutshell from the first paragraph. I even think it's sensible
that Humanist got weakened, but hitting the Tolerance ideas is probably the worst way to do it. Unless I'm very mistaken, it's completely irelevant for some of the strongest religions (or tag/religion combinations) since they can still reach +3 Heathen tolerance - Tengri (w/ yellow shamanism and Hindu or Mahayana as syncretic faith) and Indian Sultanates (+4 heathen tolerance when at 100 Legitimacy, which is sufficient) just laugh at these silly balance efforts.
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Finally: What's so great about the corruption mechanics, anyways? It's just a money sink with a fancy name, unless you get to the point where you can't pay it down anymore. It either trends towards 100% or to 0%, it's not something you
play with, it's just something that you pay down. You could just replace the corruption caused by OE by an equivalent monthly gold cost and have practically the same effect on gameplay.