I'd debate Berry Growing, Poke Radar, and Wardrobe completion more as extras rather then post-game content as those are more towards adding to a particular experience rather then being their own full-fledged feature. For instance, you don't really get much out of completing your clothes selection compared to beating the Battle Maison (especially if you're a boy as it's much more restricted). Friend Safari kind of falls into that, but it's more like the Safari from previous games so it's more eventful then those three.
I only included those because Elena90 mentioned breeding, which I'd put as being about on par with those (at least in my eyes).
Listen, you gotta remember these things; always avoid claims of Fennekin being (or becoming) part Fighting-type, don't tick off mods, and NEVER (and I mean NEVER!) suggest that Arceus is the God of Pokemon when Endolise is online. If you somehow make this mistake, run for the hills before he attempts to murder you via tongue lashing.