I installed a broken Wii Menu version, and I need help to fix it if possible

[KleinesSinchen]

but I think they consider their products more disposable than we do...

With work being very expensive nowadays and mass-produced products not… this is suggesting itself.
However, Nintendo did actively repair Wii consoles and not only send a replacement unit. They also had a price list for various defects on (3)DS consoles (screen, motherboard, charge port…)

Especially spontaneous software errors or update failures with perfectly intact hardware scream for an easy method of reflashing the NAND to default. It takes 2 minutes of work to start, 15 minutes of waiting and then 2 minutes work again (testing). That is cheaper (warranty cases) and easy money (out of warranty repair).

Looking at the passion they seem to have fighting against homebrew (and I mean NOT fghting piracy – just "unauthorized software" as they call it), Nintendo went as far as producing software just for searching traces of homebrew:
https://hackmii.com/2010/04/check-disk-for-pre-repair-process/

On a side note: They were skating on very thin ice charging ridiculous repair prices for finding a "software hack"
https://hackmii.com/2009/04/warranty/

 

[borissaid]

Savemiifrii may work if you have a Wii with GC ports and a GC controller. You'd also need a game disc with a newer system menu of the proper region on it so it can run an update from it.