Yeah, no kidding. Even for Ash, he was too stupid in that region, literally not telling Iris apart from an Axew in their first meeting. At least in Indigo League, most of his stupidity can be excused for mere inexperience on his part, not Unova, though (in fact, the only one who came across as even more of an idiot than even Unova-era Ash was Cameron, who was pretty much the reason why Ash decreased in rank during the Unova League, thus potentially rivalling Hoenn as having the worst league turnout EVER [the other leagues at least had Ash increasing in rank, Unova and Hoenn aside, and even Hoenn had Ash staying at the same rank as in Johto, the immediate preceding league he was in, and in the case of Kanto, that was just his starting point.].). And I wasn't fond of resets either, even in Unova and Hoenn (though at least Hoenn had a bit of an excuse due to Pikachu coming down with a cold at the worst possible time).
Well, to be fair regarding Brandon, him being present actually DOES make sense considering that, since he had gone through the trouble of trying to hunt down the other three Regis (even trying to hunt down Regice during the times Ash hadn't beat him yet), he probably would be the type to just be hunting down Regigigas and arrive there. At least it's better than Dawn's cameo in BW, where she literally had no reason to even BE in Unova in the first place since there was no Pokémon Contests (and besides which, I don't think it was stated that she had even finished Hoenn yet at the time, which implies she interrupted her own goal and left mid-region, something not even Ash was known to do [I'm not counting the Kanto reunion arc in S&M, as that was specifically organized by the school as a field trip for the class Ash was in for the 25th anniversary, meaning Ash had little say in the decision.].).
