Please do us all a favor and reread the article. Half your arguments aren't really too problematic.
Trinity lost 30 ap for +10% CDR. 30 less ap isn't hurting your ability to kill the enemy, however +10%CDR will make you able to use said abilities more often. Also it did lose a few points on some other stats, but it gained an additional 10% crit chance.
Brutalizer was replaced by Last Whisper which is essentially an improvement since a flat 10 armor pen is not going to scale into mid game as well as 30% armor pen on an item which can be made into another item which then has 40% armor pen.
Some of the AP items were buffed to compensate the increase in cost.
e.g.
Others were increased in cost and/or nerfed to make them less of an early game power spike.
e.g.
And a few were given a reduction in their costs without being nerfed, some even were buffed as well.
e.g.
Another point is that I believe RIOT is trying to make Mejias more of a common build item, not just that only if I am doing great, high risk high reward item. That item got so many buffs for no additional cost.
Lastly, AD based, non tank/juggernaut champions (specifically marksmen and some assassins) were struggling to make as great of an impact on the fighting half of the game due to the Juggernaut update, the armor update, the AP buff/rebalance update, and how the current meta has basically made it so that you most likely have a true or a %health scaling damage dealing top laner and/or jungler in every game (these destroy marksmen with low health pools. ex: fiora, she destroys most marksmen since she can chase them, null their cc, and hit them for true damage if they don't have a kit built around maneuvering like tristana does). So yeah, ADC(Marksmen) needed a little boost to become more relevant again in fights and not just be there to take towers quickly.
(they also stated that they were open to readjustments in necessary)