Barry Vs. Paul was unceremonious and disingenuous to Barry. I understand him losing, but he should have been able to put up a better fight than that.
- The inclusion of Hitmonlee and Skarmory was incredibly random and unnecessary, especially as the writers were doing well with keeping Barry's team consistent with his game counterpart's. Which I was a large fan of because it's one of the best rival teams due their diversity and individual strengths.
- Barry not knocking out a single one of Paul's Pokémon (but having his Skarmory, of all Pokémon, be one shot) undermined everything he did to even get in the Pokémon League. They couldn't have even given him one victory? The writers having Ursaring endure all of those Fighting attacks from Hitmonlee was incredulous. As was Empoleon's big moment with Torrent, which Paul dampened with Protect.
- Back to your point, they could have had Ash fight Barry instead of Nando, to give him a more impactful sendoff and final battle. It also would have been a callback to their first 3v3 fight when they first met; nothing of value would have been lost by having Paul defeat Nando (it'd actually be quite funny that he was knocked out of both major tournaments by Ash and Dawn's main rivals, respectively).
Well, Barry was one of the trainers who took the free badge from Sunyshore Gym, right? During the time when Volkner was unenthused about battling.
Perhaps the writers just want to hammer in the point that Barry was unworthy since one of his gym badges was not earned, the same way people view Ash's first league loss.