There's nothing inherently wrong with friendly rivals. The only ones that's really awful is Hau. And that's because he's an utterly worthless character with no redeeming qualities, has a terrible team, and is a complete and total idiot.
The real reason people like the jerk rivals is because its been so long since we've had one in the mainline games (Gold and Silver came out in the NINETIES). And so people just got tired of the friendly rivals because when you have the same dynamic over and over again it gets boring. If every rival was an asshole everyone would be sick of that too. Add onto that that the "jerk" rivals have better teams and are more powerful than their friendly counterparts, with Barry as the only exception.
Serena should have been powerful, but Nintendo seems to have actively made her a joke, saddling her with both a mediocre at best team, and also just three or four Pokemon for the ENTIRE game. By comparison Blue (and Barry) had four Pokemon by the second gym. Same with Cheren and May really.
And like I said, Hau is just terrible in general.