Why are there so few third-party games announced for switch 2?

[Mummelmann]

The Switch has sold insanely well, the same can't be said for the 3rd party software overall on the platform. 

In the top 30 all-time sales list, only 3 titles are non-Nintendo titles or franchises (Monster Hunter, Stardew Valley, and Minecraft). Minecraft having surprisingly low  sales at around 6 million also shows us something about the overall interest level of 3rd party title shoppers on the Switch (heck; I think it even passed 2 million globally on the Vita with its poor installed base). No 3rd party game besides Minecraft seems to have sold beyond the 5 million mark on the Switch, only a handful managed 4 million. Meanwhile, a whooping 21 1st party titles have sold 12 million or above; that's 21 titles selling twice or more that of the highest selling 3rd party game, that's too much not to be pegged as a significant trend on the platform. 

In the top 100 list, only 23 games are 3rd party, of which almost every single one is an Indie title, puzzle/board game, or rhythm game. The odd title which falls under more classic AAA, or at least AA status, are titles that barely scrape above 1-1.5 million in sales (RE: Revelations Collection, Dragon's Dogma 2, Dark Souls: Remastered, are among those).

Nintendo platforms are sometimes insane money-making machines, for Nintendo, but their strained relationship with 3rd parties is well-known, and not built wholly on spite and childishness (as many would otherwise tell you). The Wii and Wii U had the same issue when it came to selling 3rd party titles, this simply has not been Nintendo's strong suit since the early nineties and back.