200 people is tiny for what they are doing, especially when other triple-A series such as Assassins Creed are over 1,000 strong in manpower. Even Breath of the Wild was done by 300 devs (key word being devs: not artists, composers or writers) over the course of 4 years with secondary studios such as Monolith Software (Xenoblade) assisting. Even then those titles didn't have the burden of eventually including 1,000 unique characters into their games (Pokemon, trainers, NPCs). Whether Witcher 3 was made by a smaller studio or not is irrelevant, it's a false equivalence. I don't think it is ridiculous to expect the studio to give these games a bigger team and budget considering the jump from 3DS to Switch, especially when Pokemon is one of the highest grossing kids brands in the world.
Battle Frontier isn't a thing anymore true, it was replaced by the Battle Tower which doesn't seem to be returning either. Even so, the series has continued to give players challenges and content to play with both during and after the main story has concluded. All these aspects of the Pokemon experience has been retained in some form over the different generations. Having talked about the games with people who are avid Pokemon fans they expect these features to be retained in some form in every game as they feel they would be solely missed.
As for their preparation, well the proof is in the pudding. They are planing to release what many are calling an incomplete Pokemon game. They should have planned for this in some form but instead they continued to bloat the series with two generations per DS causing the number of Pokemon to increase exponentially as the simple hardware and 2D graphics meant they didn't have to worry about detailed models or detailed animations when adding Pokemon to the games.
The numbers support the argument that technological advancements have been a big enough issue in slowing Game Freaks ability to expand their series in its main entries. Gen 1 (1996-1999) (Game Boy, 2D Pokemon, 1 Game, 4 Versions) - 151 Pokemon Gen 2 (1999-2001) (Game Boy, 2D, 1 Game, 3 Versions) - 251 (+100) Gen 3 (2002-2005) (GBA, 2D, 2 Games, 5 versions) - 386 (+135) Gen 4 (2006-2010) (DS, 2D, 2 Games, 5 Versions) - 493 (+107)
Gen 5 (2010-2012) (DS, 2D, 2 Games, 4 Versions) - 649 (+156) Gen 6 (2013-2014) (3DS, 3D, 4 games, 4 versions) - 721 (+72)
Gen 7 (2016-2017) (3DS, 3D, 4 games, 4 Versions) - 809 (+88)
The move to 3D coupled with expansions now being over shorter time frames than in generations 3 & 4 has only worked against being able to evolve the series in a manageable capacity. The Nintendo DS alone added 263 new Pokemon thanks to Black & White going in the brave direction of forcing the players onto a clean slate of Pokemon until they had finished the game, meaning they had to design more new Pokemon than normal. The studio clearly isn't dealing well with the bloat if the E3 build of Sword & Shield along with the dev interviews are anything to go by.
I see this opinion a lot online but the series did seem to peak at gen 5 in terms of being able to match the creators ambitions for what they wanted a Pokemon game to be. I'm not going to say it should have been on the 3DS but in terms of time frame it did cover a shockingly small number of years considering how many Pokemon it added, they really should have made it last longer if only for the sake of making things more manageable on later systems.
I don't think it would have been a bad thing had the Ruby and Sapphire remakes appeared on 3DS first as a gen 5 game, it would have allowed them to get to grips with the hardware while not being burdened with the new Pokemon, least we forget that X & Y were heavily criticised for their lack of optimisation and were unable to display the consoles 3D mode during Pokemon battles (Game Freak have always had a questionable record for programming and optimisation).
I think where the series first went wrong was deciding that all Pokemon should be available in every game. The idea of the differing Pokemon regions is that, much like real animals, there are Pokemon that can only be caught in specific parts of the world. However the Pokemon universe doesn't have any rules on which Pokemon can be taken where. It's not like Australia where they prohibit certain animals from entering the country due to the eco system.
Although it would have been bad for business this would have been the best way to manage the bloat while also making the games better balanced in competitive play due to the smaller pool of monsters. Game Freak are claiming that balancing is one of the reasons for reducing the number of Pokemon in the new entry but it is far too late for that and players simply are not buying it as a reason. The games containing every Pokemon is normalised at this point and even missing one of them could be considered a failure among the fan base.
Quite frankly it is your rebuttal that fails to pass the sniff test when the product we saw at E3 shows these are real issues affecting the game. Game Freak are not equipped for what this game is and they definitely aren't equipped for what their audience expects it to be. They wouldn't be the first studio to fall on hard times following the demands brought on by a generational jump.