Party of one did it for me, seeing Pinkie's meltdown like that is NOTHING G1 would have done. She isn't just an upset pony that thinks her friends have abandoned her, but you see this sort of fragile psyche Pinkie can have. Especially since she reacted in such a drastic and dark way. It went towards a dark way showing the tea party, not just Pinkie's dialogue and tone, but the complete change in her appearance, she wasn't the Pinkie Pie we all know and love in that moment.
Overall the show in general is nothing like G1, the story telling is fun and creative, and appeals to an adult audience as well. Watching the first two episodes of season one did it for me, I remember being blown away by Nightmare Moon, the character in general was nothing that appeared in the G1 I grew up on or remember.