Could not disagree more. Even though gen VI is probably my least favourite gen, I think it has one of the best designed rosters of Pokemon by far. There's so many great designs - Aurorus is fantastical and slightly ethereal and looks like it stepped out of
The Land Before Time; Helioptile is adorable and a quirky new take on the Electric type; Avalugg is gruff and stolid in a way few Ice-types manage to be. Hawlucha looks comical at first but has really grown on me over the years. Barbaracle is wonderfully weird-looking. Talonflame and Tyrantrum have two of the best shinies in the whole series. Goodra is a borderline hilarious new take on the pseudo-legendary concept. Vivillon is charmingly simplistic and the pixel art design on its wings is a neat little throwback to earlier gen gaming. Noivern's sleek and nimble appearance matches its statistical frailty and the earphone eyes... I mean ears... still catch me out to this day.
It's very rare that all three starters appeal to me equally; the Kalos starters are probably the only set of starters where this is the case. All three final evolutions are based on RPG archetypes: Chesnaught is a rugged knight, Delphox is a wicked mage, and Greninja is an elegant... well, ninja. They also all have excellent shiny forms. The three "cover legendaries" are all great in their own way, too. The first Fairy-type legendary could easily have been pink and swooshy which would have alienated half the fandom, but Xerneas is imposing and majestic and has a captivating design (it's striking that so soon after having four deer Pokemon in Gen V they managed to do a fifth that felt entirely fresh and different). Yveltal is striking and oddly chilling; it's one of the few legitimately scary legendary Pokemon. The fact that both Pokemon have the same stat spread is a subtle design choice I'm quite fond of. Also, the connection to the X and Y aspects of their design are subtle and not overplayed; other than both of them briefly striking a pose resembling the letters, it's not remarked upon much in-game.
Zygarde appeals to me for its design and its abilities, but also for its mystique. We all know it should have headlined its own game, but it never had the chance to. I badly want its story told properly one day (and yes I know the anime had a stab and the manga did it far better, but Zygarde deserves a game of its own). The Pokemaniacal blog has some very interesting thoughts (link below) on what role Zygarde could play in relation to Xerneas and Yveltal, and the scope of a potential "Z" version.
Meanwhile the three mythicals exude totally different characteristics: Volcanion is tough and dynamic, Hoopa is snide and crafty, and Diancie is sleek and beautiful. All three are brilliantly designed (and, having always wanted a Fire/Water type, I've always had a special fondness for Volcanion).
Even when it comes to the mons I'm not hugely into (like Slurpuff) I still think that they're pretty decent designs. Slurpuff is rather kooky but at least looks fairly strong; it's believable that it could pull off moves like Belly Drum.
The only design I really cannot stand from this gen is Diggersby; it looks incredibly ugly and cumbersome. But that's a pretty good ratio!