This thread is really melodramatic lol. Nintendo has done surprisingly fine with their console businesses without major third party support on their platforms and that's in spite of some publishers jumping ship.
Nintendo's 1st part output is so powerful and influential, Sony and MS would never survive on their own in-house 1st party talent as platform holders (although Sony definitely has stepped up their game, but their collection of IP is nowhere near the recognizable Disney-level of star power Nintendo's collection of IP is).
Nintendo has had their ups and downs no doubt (GC/Wii U) but in most cases, they've been able to weather the storm and stay afloat, mostly on the back of their own IP and in-house talent and innovation, which is honestly astonishing. That's something you can't really say for most other video game companies.
Any other company losing that level of third part support for their platform post-SNES would've been buried, instead Nintendo showed the entire video game industry how to design incredible 3D video games in the form of Super Mario 64 and Zelda OOT. The amount of game design innovation from Nintendo, both in terms of tight hardware/software integration, in the N64-era is seriously under-looked. I'm pretty sure all those 3rd party devs who jumped ship to the PlayStation were heavily inspired by what Nintendo did in that era and still do to this day. They are pretty unique in that regard.