Eagle does not have a native Mac UI (only a terrible WINE port
I think you're out of date on that. The very first version of EAGLE that ran on Mac worked through X11, and had the same GUI as the linux version (not very mac-like, but pretty brilliant at a 1st effort, IMO.) The next release had a native Mac UI (as much as your "terrible UI contravening sensible UI design" can, anyway. Mostly that means that a bunch of commands moved from the EAGLE window menus to the apple top-bar menu. It feels pretty native to me.)
i will chase whatever OS that "best" productivity softwares can run in
Agreed, in principle. People unhappy that their $5k software won't run on their preferred $1k hardware platform are being a bit silly. OTOH, if you have one set of "best" tools that work on one platform, and another set that work better on some other platform, it is surely ... annoying (easier than it used to be, what with VMs and KVM switches and networks and Remote Desktop Environments, but still annoying.)
KiCad ... at least [is] a tool that is getting better all the time
Actually, I've been pretty pleased with the rate of improvement of EAGLE. Each new release seems to have several things that were widely requested by their community. And there are releases. Some of the other products I've seen people mention ("you can still get the DOS version of OrCAD", or gEDA to a lesser extent) are quite scary in that respect; effectively dead and unsupported.