Thank you for the info. Amazing what people went through (to mainly play Mario Kart Wii lol: https://wiimmfi.de/stat?m=24).
I have to look more into it, but at this point it seems to be too risky for me (never change a running system - if you are not an expert ).
BTW while Mario Kart Wii lost its online component, all tracks/characters are still playable offline. Other games like The Last Story or Battalion Wars 2 were much worse off. E.g. the latter featured an asymmetrical game mode ("Assault") where one player defends a base and one attacks.