Both 8th gen. NX isn't here to compete against the PS5 and Xnext, but against the PS4 and X1. Generations are defined by their timeframes. In a similar way, both the Atari 2600 and 5200 are considered 2nd gen consoles.
This isn't an early next gen console. Nintendo basically cancelled the Wii U after launch and now they are releasing a new and reasonably late 8th gen device.