The Gamecube era was when we really see games for Nintendo being subject to serious crunch. Super Smash Bros. Melee is the most notorious with Sakurai working himself almost to death. Rogue Leader was also developed in a really short time to make it for the system's launch.
There are people who work better under pressure, and there are people who don't. Subjecting employees to that sort of crunch is bad, but people who do it on their own because of their dedication to their craft like Sakurai should be commended - though maybe they should also be encouraged to take better care of themselves.
What Retro is doing has been a mystery. They helped a lot with Mario Kart 7, but there's been no word on them helping with any other games since then. My 2 theories are that the move from the Wii U to the Switch may have affected them more than other studios and the game may not have been as suitable for the newer hardware, or they were working on a franchise that Nintendo lost faith in and so cancelled. There was a rumor that they were working on a Star Fox spinoff, but after the failure of Star Fox Zero they may have cancelled everything to do with that franchise.