Reggie is right and wrong here. In the case of Red Dead Redemption 2, this is certainly one of the games that wouldn't have been made for the Switch in any case. Rockstar clearly wanted to push the boundaries of the other consoles so they wouldn't have considered a Switch version even if the Switch had been revealed a year earlier.
But in many other cases, his explanation is correct. The Switch is not going to get those huge western AAA titles. But it doesn't need to, so that's not a problem for Nintendo. 2019 already has a few decent third party (even exclusives) revealed. And that's all Nintendo needs to fill the gaps in their line-up.