Is Friendship Is Magic actually postmodernist? It depends largely on how you define the term. Specifically, it depends on where you feel the New Sincerity movement lies, because Friendship Is Magic is clearly a part of it.
The New Sincerity movement can be summed up as a rejection of cynicism and detachment and an embrace of intensity of feeling, exaggeration, and overt sentimentality. Some examples of works that embrace a New Sincerity aesthetic (other than Friendship Is Magic, of course) include Tengen Toppa Gurren Lagann, post-2005 Doctor Who, and Captain America (the recent movie). They reach directly for a pure emotional response while being completely open about doing so, aware that that the audience can see what they’re doing. It is impossible to watch Gurren Lagann without realizing that it wants you to think it’s awesome, but it’s so much more enjoyable if you just let go and feel how it wants you to feel, instead of trying to retain a sense of ironic detachment. Likewise, Friendship Is Magic is openly trying to create warm fuzzies. There’s no subtlety to it at all. But if you let it make you feel warm and fuzzy, the experience is simply wonderful.
And that’s where the dilemma comes in. If you define postmodernism as being about ironic detachment, then obviously the New Sincerity is a rejection of it. But if you define postmodernism (as I do) as being about conscious awareness of the construction of meaning, then the New Sincerity is all about that; it relies on the audience recognizing what the work is trying to do and agreeing to participate.
So I stand by the assertion that Friendship Is Magic is postmodernist, mostly because I think metamodernism, post-postmodernism, and New Sincerity (which are more or less different words for the same thing) are actually offshoots of postmodernism, not rejections of it.