Remember when Boots lost 25 Movespeed?
Tier 1 Boots used to give +50 Movespeed, making them almost mandatory as a starting item. It was a system-wide change to fix this, giving every single hero +25 Movespeed, and taking -25 Movespeed from boots.
RIght now we have a similar situation. Everyone used to get a 'lot' of free stats via the Mastery system, but Riot removed the 'free stats' in exchange for capstones. However, the combination of +Flat Pen from lvl 1, and the disproportionate slant of offense to defensive options present in the new mastery system have rendered the game significantly more "glass cannon" than before.
Thus I propose a solution. Give everyone +5 Base Armor and Base MR, across the board, and balance from there.