https://en-americas-support.nintendo.com/app/answers/detail/…
From March 2023, no new eShop purchases on Nintendo 3DS and Wii U can be made, and download codes can no longer be redeemed after that (this includes the Pokemon Game Boy cards you can find at EB Games to be redeemed on Nintendo 3DS for example). Redownloads for already purchased games can still be made though (just like on the Wii back in the day when the Wii Shop was closing).
Regarding Pokemon Bank (a way to be able to transfer your Pokemon through older generations), that will be made free, but you will need to have downloaded it before the eShop closes: https://twitter.com/SerebiiNet/status/1493768777007308800
End of an era.
At least they aren't pulling the plug on online servers yet
Still occasionally play Mario Kart 8 on Wii U which still has an active playerbase (also no online paywall unlike Switch)