The thing with Hau is he actually plays with the whole "friendly rival" archetype quite a bit. Under his laid back personality and addiction to malasadas, he's actually quite competent, as shown in the battle right when you first get to Ula'ula Island. Not every NPC trainer would've had the foresight to use the previous town's stone shop to buy the necessary items to evolve their Pikachu and Eevee, including specifically picking an Eeveelution that has an advantage against your starter!
But Hau gets even more interesting once he starts undergoing character development. He takes it hard when he fails to prevent Lillie from being captured, feeling like he's way out of his league. From there on, he realizes that he needs to take being a trainer more seriously if he ever wants to become a kahuna like his grandfather. It's an interesting flip from the usual "abrasive character learns to lighten up" fare.
I figure more people want jerk rivals because we grew up with them in the first couple generations, but this is a case where they're missing out on something interesting just because it doesn't match up with the first example they ever experienced.
I don't mind friendly rivals as much as most folks seem to, but this is spot on Hau. It always sucks seeing him get ****ted on even though he's one of the better developed characters, and one of the few characters Ultra actually improved by making him a Champion at the end.
As for the rest, I feel like the Kalos rivals are mostly to blame for people really getting burned out on friendly rivals. They were all extremely bland and one note (Trace seems to be the same,) previous rivals had at least a character arc or an edge of some sort. Cheren falls in line with the Blue-type of rivals more than anyone else, Bianca had an actual arc about becoming independent, Barry wanted to surpass his dad and was pretty intense all around, Hugh's entire plot is wanting to get back his sister's stolen Pokemon and is taken mostly seriously and, of course, there's Wally who starts out as a meek kid who can't even catch his own Pokemon to an Elite 4 level trainer (even if he's underutilized.)
Really, the only friendly rivals I'd say are outright bad are Gen 3 Brendan/May and the Kalos group. I say Gen 3 for Brendan/May because ORAS improved them by a fair amount.
But I'd still like some "edgier" rivals every now and then. I mean, look at Gladion, he was a jerk for a decent portion of the game and they still gave him a compelling character arc and he was very popular even before the game had come out.