OS X Yosemite, why block my view when you should’ve known better?

I now frequently experience several apps freezing for no apparent reason. Standard apps like Finder.app, Preview.app, or Mail.app or Safari.app, would just stop responding. After digging it up a bit, I found out that when Spotlight get into such an aggressive reindexing, Finder.app also stops being responsive. My conclusion, from here, was that, some of the standard apps that ship with OS X Yosemite contain a certain amount of code that are very old or simply badly designed. Such code, typically the work of UI framework enthusiasts or design principles of another era, would traverse a UI layer stack for tasks like disk and network access, although they shouldn’t have to.