Why turn Ryze flat MR reduction into percent MR reduction?

It completely changes his aim, instead of deleating squishies he is now a Tank buster.

Also negative MR was such a healthy game mechanic, stacking it was great for magic damage teamfights, but it was also easy to counter, now witzh both Soraka and Ryze having lost that ability, just another alternative playstlye has been removed from the game. Yay for homogenisation -,-

Also what is the point of flat reduction being the only thing able to go negative, when it is applied first and you can never get enough to actually go negative.