How does the new system compare to the old in regards to tech disparity?
Is there a bigger or smaller gap between Europe and the ROTW? And does the gap surge earlier or later?
Overall, have tech costs increased or decreased?
AIs pays more for techs across the whole game, like more 5000-10000 mana points than before. This AI mana isn't going to ideas, deving, coring etc. So AIs got massively weaker by this change. They neeed more time to get to the same point than before (time gets those lacking points).
I think this is just an unintended effect of the change. Hard to imagine devs trying to wreck AIs and at the same time saying they're working on improving them.
As for overall cost they increased but only if you pay them. Meaning player can wait / spawn institution and then get the techs, and only pay those +15%, +30% , + 50% for essentials.
AIs pay always no matter the cost increase for techs. Before they paid accrued cost. +1%, +5% and had plenty of time to get institution. Now cost jump is from the tech and not from institution spawn. So it leads to weird situations like in my game above. You can have a situation where institution didn't even spawn yet and every country pays +50% for techs. Before this didn't even happen at all, accrued cost started only if institution spawned. And as every humans seeing this, I adapted and went behind in tech. At the same time Ais drained like thousands of mana for those +50% increased tech in Europe. So I had 21 ideas and plenty of dev, and Ais had 6 ideas on average, useless tech and couldn't core land because of those +50% increase to techs. Countries sitting with uncorred land for 20-30 years for lack of mana.
Granted this was some weird scenario where Colonialism didn't spawn right (but tech changes caused that, for colonizers payed more for tech and didn't have points for exploration ideas, so it delayed Colonialism, causing even more tech mana points drain), but I assume this is prevelent in every game but somewhat not to that extreme level I saw.
But if you got weak AI Portugal (mana ruler), and Castile is starting with those 0,0,0, then I imagine if you don't play as Colonizer yourself, you very often can get into this mess where AIs can't fill Exploration, Expansion ideas and can't even start colonizing properly. It all depends on instituiton spawn but before change this didn't even happen to begin with. And it happened in my first game so it can't be that uncommon to have delayed colonization from this tech changes. I'm in 1544 right now. No AI has colonial nations still.
This tech change is massive. You still can have games that look the same like old one, depending on spawns etc. But it causes weird scenarios that didn't even happen before.
If an AI is on institution spawn it doesn't change anything for them. Yes. But if an AI is long way from it, they pay hugely more points in comparison to old system. If those AIs have poor rulers they are basically screwed. I'm seeing countries with 4 ideas in 1544 still. They pay those +50% much more than before. Because in old system 1) AI not payed increased cost for techs if institution didn't even spawn -> now they do, 2) AI not payed those increase prices right away. They had time to take techs with discount that was smaller with time. -> now they don't have that time.
And as an AI has no idea how to circumvent this problem, they just take +15%, +30%, +50% costs. I have like majority of countries in Europe take +50% costs for tech. This was never the case in like 8 years of EU4. PDX just achieved new level of screwing AIs.