I would say huge BGA packages are not much of a problem. KiCAD is plenty cable for laying out such a board and all the layers such dense chips require. Its mor

I would say huge BGA packages are not much of a problem. KiCAD is plenty cable for laying out such a board and all the layers such dense chips require. Its more of an issue of high speed designs, you cant easily put a layout into a simulator or have it even simply just calculate impedance of a trace automatically as you try and place them. Instead you must manual put these details into a calculator. Its things like this that really slow down working on a complex design. Although, large BGAs generally imply some sort high speed elements in a design so equating packages with needed features is not unreasonable. Also component library management could be better. Although, for simple to moderate designs its definitely starting to give other professional software a run for their money.