Remove all first party games on any console and see what happens. A console needs 1st party as well as third party to be a success. A bigger 1st party can make up for a smaller third party however, but's good to have a steady flow of both.
Anyway I don't see why the Switch isn't as powerful as any potential PS5 or Xbox Two means it won't get third party support. The Switch isn't as powerful as the current PS4 and Xbox One and it's getting the best third party support for a Nintendo console in years. If the Switch sells well, what reason is there for devs not to make titles built from the ground of or at least in mind of Switch's hardware?
For the Switch to stay competitive as a handheld it's fine for the next 8 years. I do think they'll need an updated system to truly keep the home console hybrid point going by 2025 however. I still think it would sell of course, Nintendo's handhelds do amazing. I just think the home console side would be very hindered compared to the handheld side by then.
Remove all Vita first party games and everyone don't care, they bought it for third party JP games