The inabilities of Japanese third parties to respond their own market is of their own doing but also, frankly, largely overblown beyond the likes of Capcom, Level5, or globally successful companies like Bamco.
The Switch itself has seemingly not been at a loss for wear at the absence of these titles and is selling on its own USP and Nintendo's software (and still moving 3rd party software). That is a very, very strong wind on which to ride into a future of software titles like Pokemon, Animal Crossing, Smash, and, later, price drops. We'll invariably see forms of DQ also appear as have even been announced.
Moreover, the above shows just how irrelevant most third parties have made themselves in Japan. They've completely demolished their own mindshare and relevance, and frankly I don't see many of them making any actual successful inroads into "the west" or Asia or Mars. We're more watching the slow and steady march into oblivion and a handful of exceptions that like to be celebrated.
MHW would have maybe mattered years ago, but we're looking at fairly bleak 2018+ for the PS4 in Japan beyond this title and the system has already plateaued, its down hill from here out. In the West, the PS4 will go on chugging for a year or two more. The basis of Oregano's argument either supposes that the PS4 will somehow not atrophy in audience as it ages-out but that also the PS5 will replicate it without further considerable declines. Otherwise, he's arguing that... a franchise dropping millions with millions still sold in Japan will be sustainable when it drops another million and then another five-hundred thousand and then....