Both Sun and Moon and Omega Ruby and Alpha Sapphire were developed alongside X and Y. Arguably the emptiest, prettiest and shallowest games. Had a decent backstory (AZ's War), a respectable villain (a genocidal prince) and an amazing post-game (Emma! <3) but let's not act like having more people would've allowed for them to put more content into the games during the development time, which was confirmed to be since 2010, alongside Black 2 and White 2, meaning every single time they decide to divide the workload, one game suffers.
And now we're in a situation where Ultra Sun and Ultra Moon, Let's Go Pikachu and Let's Go Eevee and Pokémon Switch were almost certainly all under development at the same time. USUM were decent like ORAS were. LGPE look amazing (for remakes) like SM did. So who do you think is the most likely to suffer? I know what my guess is.
I really doubt that Sun and Moon's development period intersected basically at all with X and Y, first of all - there's no reason to conclude that. That X and Y in turn were being developed at about the same time as B2W2, on the other hand is... fairly straightforward and to be entirely expected. One was the first of a generation, typically handled by one team; one was the latter end of the previous generation, typically handled by another. Sun and Moon, however, likely were picked up after a third version or second paired set from Kalos was scrapped, which itself likely didn't enter development until after X and Y were ready for release given that ORAS were being developed in parallel to X and Y.
And no, more people does not always equate to more (or better) content. Coming from a development perspective myself, albeit not in video games until I have a change in career, I can tell you that a huge team often just means people are left doing nothing, or too many ideas get thrown at the project and the good ones aren't even heard. It's not something that conventionally benefits from legions of people and dozens of groups - it's an art, like writing or music. There is a finite number of people that properly work together to make it a truly good experience.
Following that, I want to also point out that a lot of people seem to have been very happy with Kalos. These pretty, shallow, and allegedly empty games are the best selling on their system, the best selling of the post-DP half of the franchise, and are pretty well liked by a large number of people. As someone above noted, their intent was never to make the games challenging, or pro-level, or whatever it is that the more vocally negative sect of the fanbase claims to have wanted on whatever day they're critiquing the game.
The franchise, at its heart, tries to be about the adventure and about bringing real-life players together. Kalos did that really pretty well in the end, didn't it? Regardless, we know XY certainly wasn't a set of games developed with all that much regard or concern for any of the things for which they're traditionally criticized, like ease or lack of a post-game. That much has been made abundantly clear by the devs.
The 2019 game is most likely going to be a rushed, incomplete mess of a game.
As stated above, this is a totally unsupported conclusion.
I want to know exactly what it is everyone wants out of these people. We already know that there are multiple teams that work on different games - it's literally almost always been that way, so there's no real argument that the simple fact LGPE exists is detrimental to the development process of the 2019 titles. Those titles, in fact, will have been in development for a bare minimum of two years at the point that they're finalized, and more than that by the time they are released. We have well over a year to go and it's been nearly a year since their announcement, if we take the E3 statement about a "proper" Pokemon RPG to be referring to those games.
We know nothing about the coming titles besides the fact that LGPE are supposed to be more casual than them, more "join us!" in their orientation and purpose. That suggests that the 2019 games are... well, literally what we've gotten for the past 22 years. And nothing more or less. It doesn't suggest that they're going to keep any changes made in LGPE (and rather suggests the opposite), and it doesn't give any further information.
The 2019 games could be the "hardcore" fans' biggest dreams all wrapped up into one thing - more difficulty! a Battle Frontier! more post-game plot! a deeper and better written story! situationally appropriate facial expressions! - and we wouldn't know. They could be abysmal, horrid stains on the franchise's legacy, sure, but in the absence of proof of that the logical thing to expect is probably just the average of all the good and bad from the past seven generations (so like, Sinnoh or something, I guess).
Spending as much time as XY and SM on exponentially more intensive hardware with twice as many games in between certainly isn't doing it any favors. Looking like it'll be the same as or worse than those two.
The confusing part of this statement, in my eyes, is that you've equated XY and SM. Not to shoot down your personal opinions, but I thought SM was widely regarded as the beloved critical darling of the latest several generations, while XY was criticized for its ease. I don't think most people (besides me, actually, as I loved both) would put them too close together in quality, and I know a lot of people would love for the 2019 games to be as good as Sun and Moon.
Anyway, see above, but also note that more intensive hardware doesn't always mean its harder to develop for if the appropriate tools are acquired; there are a lot of Switch titles and ports that were developed for higher-standard hardware than the 3DS that are technologically inferior to the 3DS Pokemon games, or less complex, or just not as good regardless.
Say it's possibility if you want, I won't deny that, but there's no reason whatsoever to be saying it's likely.
And honestly, I don't think X/Y's and Sun/Moon's problems had anything to do with time or resource constraints. Game Freak has made it clear that it was their goal during those games to provide a more simple experience. The lack of content, for better or worse, was purposeful. We have no clear reason to think that Let's Go Pikachu and Eevee will cut into development time and resources for the 2019 games. Also, we have no idea how long they've been working on the 2019 games for. It seems pretty clear to me that the Let's Go games were, at least in part, made as a way to buy them more time to develop those games. There's just no reason to worry yet. Maybe things will turn ou
t horribly, but we just can't predict that now.
Yes! This!
I personally think Let's Go has been in some form of development - probably conceptual for a while rather than physical, of course - since Go was released and became a smash hit.