No, try again. That isn't what defines it as.
A new set of pokemon in a new region is what starts the generation.
Any game release after that point is part of that generation until the next game with a whole new region and new set is released.
They are by definition of Generation Generation 8.
They do not need a Generation 8 pokemon to be Generation 8.
Peace is a lie. There is only passion. Through passion I gain strength. Through strength I gain power.
Through power I gain victory. Through victory my chains are broken. The Force shall set me free.
–The Sith Code
Except your own source contradicts itself.
"The core series[1][2] of the Pokémon games or core games[3], commonly referred to as the main series or mainline games by fans, is the game series for Nintendo video game systems, which follow the standard model of a player's journey through a specific region to catch and raise Pokémon, battle Trainers, fight crime, and earn recognition (usually by collecting Badges from Gym Leaders) until they are acknowledged as the strongest Trainer."
Considering Legends: Arceus is set in a time before Humans and Pokemon co-existed, it's extremely unlikely that there will be a lot of trainer battles let alone Gym Leaders and an Elite 4.
Hence why, even though Colisseum and XD: Gale of Darkness have a very similar gameplay style as the Main series, they are not main series games.
Peace is a lie. There is only passion. Through passion I gain strength. Through strength I gain power.
Through power I gain victory. Through victory my chains are broken. The Force shall set me free.
–The Sith Code
It doesn't really contradict itself. As we know not a lot about it even now. I mean in Sword and Shield can you really even say you fought "crime." Team Yell is more just trying to keep you from progressing so Marnie can win. And Marco Cosmos is only fought when they are trying to prevent you from interfering with Rose talking with Leon.
Peace is a lie. There is only passion. Through passion I gain strength. Through strength I gain power.
Through power I gain victory. Through victory my chains are broken. The Force shall set me free.
–The Sith Code
Except if you are playing the Gen 4 remakes, you are playing Generation 8.
And if you are playing Legends Arceus, you are playing a main series game.
These have accepted definitions. It is like saying your favorite pseudo-legendary is Haxorus because you define pseudo-legendary differently than what is accepted.
Peace is a lie. There is only passion. Through passion I gain strength. Through strength I gain power.
Through power I gain victory. Through victory my chains are broken. The Force shall set me free.
–The Sith Code
Bruh, I'm not gonna do this hypothetical shit. Fighting crime is only one part criteria. Battling trainers, fighting Gym Leaders, and becoming acknowledged as the strongest trainer is also part of the criteria, but once again, what we know about Legends Arceus is that this is a time where humans don't fight alongside Pokemon, so it's highly unlikely we'll have those things in this game. Sure, it's possible that it will happen, but based on what we know 5 months before the game comes out, that isn't the case.
They are by definition Generation 8.
As the last game that introduced both a new region and new pokemon were Sword and Shield and no new region and set of pokemon has been introduced since.
They do not require Sword and Shield mechanics or pokemon to be Generation 8.
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Yes, but that is just also a rough description of what is generally considered to be main series. Prior to Sun and Moon release, main series was believed to require gyms. We now know that isn't the case. And with Sword and Shield, we also know an Elite 4 is not necessary either.
Peace is a lie. There is only passion. Through passion I gain strength. Through strength I gain power.
Through power I gain victory. Through victory my chains are broken. The Force shall set me free.
–The Sith Code
Peace is a lie. There is only passion. Through passion I gain strength. Through strength I gain power.
Through power I gain victory. Through victory my chains are broken. The Force shall set me free.
–The Sith Code
The Ranger games at least have one-way connectivity in the form of mystery gift pokemon. Mystery Dungeon is an independent spin-off series.
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The Pokemon in gen 2 are so bad, even the Johto gym leaders don't want them! Recycle job.
Thanks for the ad-hominem; it supports your inability to support your argument.