Rewatched the entire Ash era.

Of course, nothing is TRULY "objective", but all of the universally agreed "subjective" qualities will be omitted:

•Animation 

•Art Style

•Humour

•Personality 

•Compatibility 

•"Underwhelming", "should've caught...", "arc should've ended differently", "what-if"...

•FILLER -

1)Every arc has FILLER

2)A lot of viewers like filler

3)FILLER can be considered world-building

4)The mere existence of "filler" is debatable

Note: JUST BECAUSE ONE ARC HAS MORE FLAWS THAN ANOTHER DOESN'T MEAN IT'S WORSE. 

This is still ultimately an opinion.

Clarifications:

"Pity badges" - I hate them too, but they're part of the story, not a flaw. Ash not earning badges is why Charizard disobeys him, and why he lost the league. 

Max is actually a decent character in AG, and we're not judging by personality.

Pikachu does get nerfed in nearly every arc, but XY's nerf is much less than prior. He's lost Surskit, Korrina's Lucario, Clement's Luxray and Wulfric's Avalugg (after 1 win each), Sawyer's Sceptile and Alain's Charizard (after 2 wins each). 

Of these, only Surskit is really bad. 

If DP Pikachu only drew with Elekid and lost to Roark, it'd only be a minor flaw too. But losing to wild Buizels, struggling against Magikarps and Prinplups, and getting hospitalized by a rando who couldn't reach the league is just too much. 

Brock DOES do more in DP than Johto and AG, but nowhere near enough to justify his main character status:

•Dress up contest and Tag tournament were nice, but had 0 relevance to his doctor/breeder goal 

(Even Johto Misty's Seaking/Whirl Cup were relevant)

•Croagunk fought Saturn, Brock had no input

•Has 2/3 scenes with Paul - had no effect on Paul's development 

•has 4/5 background scenes of helping out Nurse joy - never the focus of an ep until end of DP

•Sees Uxie's SHADOW once, then never sees it in person until the last episode of the finale. Doesn't travel with it, bond with it, or even feed it.

Alola group isn't meant to have equal status. Even still, the more "minor" of the 6 actually have more focus than most of Ash's prior companions.

Personal thoughts: 

Team Rocket are usually the worst thing about the anime. The sheer amount of world-building, battles and character development we missed out to see them "blasting off agaiiiin!" for the 10000th time is ridiculous.

Johto-XY is RIDICULOUSLY repetitive - up to the league, you can predict everything that'll happen (gets 1 starter minimum, reach gym, win 1st or 2nd attempt, get badge, travel to next gym, blast off TR in between gyms, get full party, occasionally fight regional villains, reach league). 

XY tried to change things up, but didn't go all out.

The series is WAY TOO Ash-focused. Even shows with the MC's name in the title let the other characters take the spotlight (Naruto, Yu-Gi-Oh). 

Nearly every important thing has to involve Ash, and if it doesn't, it'll be secondary to Ash's stuff (Grand Festivals are never given NEARLY as much attention as Leagues).

The sole exception is Goh, and everyone hated him for challenging Ash-dominance. (I believe this is why the fanbase hates dual-protagonists, since they don't get the concept of one character NOT hogging everything).

TR were only "good" characters in BW and SM. Everywhere else, they're plot devices.

Optimal TR screen time is around 50%.

BW-JN (yes, even BW) was FAR easier to binge than Johto-DP. The animation, TR presence, and pacing are infinitely better. Can only guess they were threatened by the rise of streaming in the 2010s.

No Ash series should've ever passed 3 years (and even that can drag).

XY angered me the most - it was so close to perfection:

.First showcase in ep 40 instead of 60 

.2-3 more Showcases for Serena to lose

.Full Astrid battle for Noivern/Goodra

.Maybe reduce TR eps by 10%

Most of SM's common criticisms are subjective

Despite what this sub says, Horizons is objectively better than Ash-era in nearly every way - consistent characterization, pacing, unpredictable plot developments,etc.

Its biggest flaws are mere nitpicks compared to things like GS ball, wallpaper main leads, unresolved Giovanni, constant personality changes, etc.

Let me know if you have any changes to propose!

"Objective" flaws every series