I have a soft spot for this episode, even though a lot of people dislike it, and it's fun that the cast got the mane 6 to play caricatures of themselves. Especially Smart Cookie being this kinda snarkily aware of how stupid Chancelor Puddinghead is, and rarity being such an over-the-top prima-donna.
I don't get why they'd hate it. After all, you could say that in-universe, they left out certain things in the retelling of Equestria's History. Lord knows we humans tend to do the same...