Nintendo own is no problem for performance of Switch, but a big problem for third parties. FF and Resident Evil are planed to release for PS5 and won't move to Switch because Switch doesn't have enough performance for their devs. At now, Nintendo has a big market, but it is unsteady as the Wii used to be. A next challenge for more big and stable market is taking in major franchises.
Third party support for the Wii and Switch isn't even remotely similar, so the unsteadiness you allude to isn't real.
You don't need to act as if Nintendo and Sony were facing pressure and problems of similar scale. It doesn't make you look biased if you say that Nintendo is in a much, much better spot, because that's the reality of things.