The original Wii supports GameCube controllers, the Wii U supports Wii Remotes, Wii U and Switch both support USB GameCube controller adapters, and NES/SNES Classic Edition Mini systems support the Wii Classic Controller. Switch Lite supports pairing Joy-Con too, despite having no rails for them.
Wii U goes so far with Wii Remote support that Nintendo usually treated it as the preferred way for extra players to join local multiplayer, moreso than its own Pro Controller. Wii games were more limited with GC controller but still supported it in a few big titles like Brawl and Mario Kart Wii.
Nintendo has repeatedly done things like this.
The original Wii supports GameCube controllers, the Wii U supports Wii Remotes, Wii U and Switch both support USB GameCube controller adapters, and NES/SNES Classic Edition Mini systems support the Wii Classic Controller. Switch Lite supports pairing Joy-Con too, despite having no rails for them.
Wii U goes so far with Wii Remote support that Nintendo usually treated it as the preferred way for extra players to join local multiplayer, moreso than its own Pro Controller. Wii games were more limited with GC controller but still supported it in a few big titles like Brawl and Mario Kart Wii.