Palmer being a Frontier Brain actually makes Barry look even less competent, since Barry was an inferior trainer than Sawyer despite having a Frontier Brain for a father. Most trainers aren't fortunate enough to have a Frontier Brain for a father to give them early experience. By contrast, Sawyer was an average beginner with no prior experience like Barry had. Its not quite as bad as Dawn being outclassed by the less-experienced Zoey (and even Nando) despite having a Top Coordinator mother.
Despite his family background, Barry got beat 3-0 pretty easily by Paul (and would have lost even faster if Paul just sent out Electivire first). The difference between Sawyer and Barry is that even without Mega Evolution, Sceptile would beat Electivire 1v1 before losing to Magmortar. The gap between Sceptile and Ursaring/Magmortar is slightly bigger than the gap between Electivire and Barry's Empoleon, so neither would damage Sceptile (let alone beat it) unless Electivire weakened Sceptile first.
Barry was introduced with a fully evolved Empoleon, and losing to Paul isn't a negative. I don't understand what you're trying to say. Sawyer was better at the end, no question, but you were talking about the beginning.
XY Ash could probably beat Barry 3-0 without even using Pikachu or Greninja, if he switches twice like Paul did. Base Greninja or Pikachu would solo Barry 3-0 either way.
Talonflame, Noivern, Ice Beam Goodra vs Empoleon?
Really?
And Greninja never 2-0 anything, let alone 3-0. We can't assume a feat like that without a similar one, and Greninja doesn't sweep teams.
I agree that Remo probably relied heavily on his Mega Garchomp, though it being a pseudo is irrelevant since being a pseudo has never meant anything past the original series. I doubt Remo's other Pokemon were completely weak Pokemon since even Sawyer had strong Pokemon like Aegislash and Clawitzer despite how strong his Sceptile was, so I'd expect Remo to have at least 1-2 strong Pokemon aside from Garchomp.
We know through observation that the anime respects both pseudos and legends; they've portrayed as rare and powerful when they've appeared, legends moreso. Special tactics, powers or sheer numbers are necessary to bring them down. Aside from Goodra, at least.
That said, you're probably right that Mega Garchomp wasn't treated as a Mega pseudo, but simply another Dragon-type Mega to flounder before Alain. It's weakness might be a reference to Mega Garchomp's lower speed, and Mega Charizard X usually does beat it in that environment.
Even if Alain's Metagross beat 4 of Remo's Pokemon, it doesn't automatically make the rest of Remo's team weak since Metagross could do the same to Ash's Noivern, Goodra, Talonflame, and Hawlucha.
needs to win.
That's possible, since Tyson's Metagross beat Grovyle and Swellow, before losing to Pikachu. Metagross IS a pseudo and pseudos are generally portrayed as threatening.
But we can't call Kalos Ash's strongest team if a pseudo can body two of his Pokemon. That happened in Hoenn, Unova, meaning the rest of the team is around that power level. Needing Pikachu to solo Tyranitar and Metagross so they don't wipe out the Flying-types isn't a good look for anyone but Pikachu.
While nobody in Kalos League was a veteran, I can say that nobody in the Kanto, Johto, Hoenn, and Sinnoh Leagues had any E4-level Pokemon aside from Tobias and DP Ash (Peakachu, Charizard, and Sceptile were only on-par with E4 non-aces). Not counting Ash of course, only Alain (Charizard/MCX), Tobias (Darkrai), Sawyer (Mega Sceptile), or Remo (Mega Garchomp) have any chance against an E4 ace 1v1, and only Alain could beat an E4 Mega Ace using MCX.
Most teams have aces or at least "boss" Pokemon. Sinnoh+ Ash has had two since Pikachu only really started to become a wrecking ball in Hoenn.
Unova Ash had Krookodile, who has better feats than Greninja, defeating Iris' Dragonite and especially Stephan's monstrous Sawk. But many of Ash's other Unova Pokemon, like Oshawott, weren't strong at all. It's perplexing to call Unova Ash's weakest team when Krookodile, Pignite and Pikachu were all respectable, no? But that is a common complaint.
People don't compare the aces, they make unsubstantiated claims about the whole team. Ash's strongest team doesn't have Goodra or Noivern.
The Kanto League was mostly beginners using stuff like Bellsprout, Nidorino, and Ivysaur, let alone most of Ash and Ritchie's Pokemon. Hoenn League never had any veterans at all since Tyson is heavily implied to just be a skilled beginner similar to Sawyer (given Tyson's close battle against HL Ash and using the same six Pokemon throughout), Morrison was blatantly a beginner, and Katie was at best equal to Kalos League Astrid (who was much, much weaker than Act 1 Astrid) and even Astrid wasn't a veteran.
Ritchie and Cameron aside, Ash inevitably ended up battling those veteran trainers as he progressed through the tournament, because veterans are more likely to win.