So, is there any reason why GO skipped Gen 7/Alola and went straight into 8/Galar?
My guess (and it is only a guess) is that Gen VIII (or to be more specific, everything Galar-related) is coming to the end of its time, and Niantic/TPC want to get as much marketing and mileage out of it as they can before BDSP happens, and then presumably after that we move on to Gen IX. Once BDSP and L:A drop, the focus is likely to shift from Galar and its associated Pokemon to Sinnoh. That means less opportunity for marketing the Galar-based games.
Consider that the anime at the moment is taking its cues more from Pokemon Go than SwSh, and it isn't solely set in one region like previous seasons have been; it's more focused on all 8 generations. That means less potential overall to market the Galar mons. This way, they get to re-ignite interest in them. It's kind of a win-win for Niantic and TPC as it's sure to lead to a big surge in profits for Niantic (people always want to raid new legendary bosses and chase new shinies, no matter how underwhelming Zacian and Zamazenta will surely be until they get access to better moves and their other forms). But there is a strange whiff of desperation about it imo.
So while I'm hoping that these few Gen VIII mons are a taster, because I'd rather have the rest of Gen V and VI instead of the Gen VIII mons, I wouldn't be surprised if they carry on with Gen VIII - or, more likely, mix VIII with the continuing release of V and VI.
Oh, wow,
a majority of the Kalos Dex is not available.
And, while I get why a majority of the Mythicals, Pokemon with multi-form gimmicks, and Kecleon & Zorua family are missing, why is Druddigon and Larvesta/Volcarona unavailable? They have no gimmicks, they're pretty normal Pokemon.
On that subject, of the Kalos Pokemon missing there's no reason why Skiddo/Gogoat, Inkay/Malamar, Helioptile/Heliolisk, Tyrunt/Tyrantrum, Amaura/Aurorus, Hawlucha, Dedenne, Carbink, Phantump/Trevenant, & Bergmite/Avalugg to be unavailable pretty much for the same reason; they'll all just normal Pokemon. Okay, maybe they'll have a little issue with implementing Hawlucha's Signature Move and Inkay family would mostly be missing their gimmick, but otherwise no issue.
*Sees Vivillon* *Prays for the souls of Pokemon GO players*
Also looking through the exclusives, I found some of them either as neat references, showing their research... or having no clue why they're like that. Think I'll make a post in the "Little Things You Like" thread about that.
The majority of the Kalos Dex is not available because we simply haven't reached it yet. Niantic has done the generations roughly* in order (including regional forms for Pokemon already in the game) so they're still getting through Gen VI atm.
But when it releases Pokemon in batches it doesn't bother with following a strict Pokedex order. The first Gen II Pokemon released were the babies and Togepi/Togetic, not the starters; the first Gen III Pokemon released were Shuppet, Duskull, and Sableye. They'd released Groudon and Kyogre before you could catch Taillow. Burmy, Cherubi, and Mime Jr were some of the last Gen IV mons released; Munna wasn't released until about 18 months after the first Gen V mons arrived.
As to why some of the Gen V mons are still absent, Niantic chose to drip-feed Gen V rather than release it in batches but then they opted to mix Gen VI in with it, which makes sense given Gen VI's smaller roster. It's not so much that Pokemon like Bergmite and Dedenne are unavailable as they are "yet to be released". At the current rate, we will probably get the vast majority of Kalos by the end of this year or early next, unless Niantic decides to switch tracks and start releasing all of Gen VIII instead.
In regard to all the missing Pokemon pre-Gen VI, there's a fairly evident reason for why each of them isn't here yet:
-Kecleon they're clearly unsure of how to implement. A lot of people suspect that the catching method will be something to do with AR Niantic is still developing
-the same goes for Zorua and Zoroark, which will likely be highly desirable Pokemon so can be saved for some sort of event
-Druddigon is a Dragon-type, which have always been rarer in Go than other types, but as a single-stage Pokemon it presents more of a challenge than Pokemon which need to evolve - once you've caught it, you've caught it. Gen V is actually fairly Dragon-heavy so they're obviously waiting for the right time to drop it
-Larvesta and Volcarona are going to be extremely desirable Pokemon when they're released so that won't be rushed. I've no idea if the fact that Volcarona sounds vaguely like "corona[virus]" is making Niantic hesitant to release it in the current climate (frankly, I doubt it) but maybe it's a factor. Data indicates that Larvesta, like Magikarp and others, will require 400 candies to evolve which is a gimmick as far as I'm concerned. Regardless, it's on par with Pokemon like Hydreigon and Dragonite and Niantic has always guarded those for an initial period.
When it comes to legendaries, Manaphy and Phione obviously present a logistical challenge (should you catch them separately? Should Phione be caught via Special Research as the penultimate stage before you encounter Manaphy? Should Manaphy be in its own special 25KM egg?) as does Shaymin. Arceus is clearly being saved for next year.
*before anyone rushes in to pull me up on that, consider what the word "roughly" means. Obviously there are some exceptions.