The biggest issue I have with the change is not being able to choose where I use the KP. More KP isn't really More KP if we can't use it where we'd like.
Understandable, but if I might share some of my insights:
Part 1 - Pacing:
Players really wanted the KP drops from AWs and tournaments to be stored so it doesn't interfere with regular accumulation.
The core mechanic of the game is pacing, which is dually controlled by multiple variables, including resources and KP.
Once a person can store an unlimited amount of KP in instants, they can eliminate KP as a pacing. With a few hundred stored KP instants*, you can blow through a newly released chapter as fast as you can acquire the resources. Then you get bored until the next chapter drops, which increases the chance you'll stop playing.
Part 2 - City-space pressure:
The devs are up against some intractable limits with the city map. Adding more graphics makes the game slower and more prone to crashing, so they've had to balance making the map larger against losing players with computers that aren't top of the line. They have a large market component that is very mature players (over 50) who are not interested in buying a new rig for gaming every other year.
Ancient wonders provide additional assets without needing more space. My mountain halls and Golden Abyss aren't even half way to fully upgraded, yet between them they are supplying over 10,000 population. My Shrewdy Shrooms and Dwarven Bulwark aren't half way, yet together they give me training size equivalent to 15 fully upgraded armouries. It is the interest of both players, and the designers, to get players to pay more attention to Ancient Wonders as the engine of their growth, instead of the tech tree. Getting players to look at AWs with renewed interest requires a carrot of some kind. Extra KP that can only be used in AWs is absolutely going to be that carrot.
Inno can't afford to have players running through the tech tree at high speed and then getting bored and quitting. they need to engage us so that we stick around and keep giving them money (or at least keep being tempted to give them money).
*My FS gets at least 8 chests almost every week, which is 80kp per person in stored instants. If the next chapter 12 weeks out, any of our players who are finished could have 960 KP stored. And in the meantime, they'd have also put 1200 kp into other people's AWs (because they have nowhere else to put them at that stage) which would get them at least another 200 or 300 in storage. They'd have over 1000 KP ready to dump into the tech tree as fast as they can obtain the resources.