I'm surprised by that figure of 24 for Nintendo games released last year. From a Switch perspective, Nintendo's games were:
Dragon Quest Builders 2[B] Square Enix Omega Force December 20, 2018 July 12, 2019 July 12, 2019
New Super Mario Bros. U Deluxe Nintendo EPD January 11, 2019 January 11, 2019 January 11, 2019
Yoshi's Crafted World Good-Feel March 29, 2019 March 29, 2019 March 29, 2019 [137]
Nintendo Labo: Toy-Con 04 - VR Kit Nintendo EPD April 12, 2019 April 12, 2019 April 12, 2019
Super Mario Maker 2 Nintendo EPD June 28, 2019 June 28, 2019 June 28, 2019
Marvel Ultimate Alliance 3: The Black Order Team Ninja July 19, 2019 July 19, 2019 July 19, 2019
Fire Emblem: Three Houses Intelligent Systems Koei Tecmo Games July 26, 2019 July 26, 2019 July 26, 2019 [137]
Tetris 99[C] Arika August 9, 2019 September 6, 2019 September 20, 2019
Astral Chain PlatinumGames August 30, 2019 August 30, 2019 August 30, 2019
Daemon X Machina[B] Marvelous First Studio September 13, 2019 September 13, 2019 September 13, 2019
The Legend of Zelda: Link's Awakening Grezzo September 20, 2019 September 20, 2019 September 20, 2019
Dragon Quest XI S: Echoes of an Elusive Age Definitive Edition[B] Square Enix September 27, 2019 September 27, 2019 September 27, 2019
Ring Fit Adventure Nintendo EPD October 18, 2019 October 18, 2019 October 18, 2019
Luigi's Mansion 3 Next Level Games October 31, 2019 October 31, 2019 October 31, 2019
Pokémon Sword and Shield Game Freak November 15, 2019 November 15, 2019 November 15, 2019
Source:
WikipediaThat's fifteen titles; and even then some of the games were just published by Nintendo rather than coded (i.e. such as the two Dragon Quest games, Marvel Ultimate and Daemon X Machina). I guess that 3DS (Kirby's Extra Epic Yarn) and eShop / mobile stuff raise the number up to 24.
I'd kinda expected more big new titles (not ports) from Nintendo themselves; I hope we see some during this year.