The artist helpfully compiled a list of their grievances:

“FLUTTERBAT, Coco Pommel, Twicane, Power ponies, Discord, TWO Winter-Wrap-Up redemptions, Wet mane Rarity, Grumpy Cat cutie mark, Pinkie’s drawing of the scores between Applejack and Rainbow Dash, the Family Guy styled cutaway when Pinkie rang the bell, Pinkie Pie, Appledash, Twilight’s a background character, Mane-iac, Spike the punching bag, obvious cliches like RD bringing up ponies randomly singing is weird, Fluttershy is now a saint and Applejack is a Satanist conservative (even though I’m liberal myself, it’s so annoying), no more re-occurring background ponies, Pinkie defying gravity and physics, Discord getting his own song, mapplelisious (yep.) and creamy, creamy frosting.