The Switch is inheriting Nintendo's home and handheld market. The DS and 3DS are JRPG powerhouses. Th Switch is just continuing that trend. Nintendo's home consoles didn't get many JRPGs after the SNES because of budget and competition. So the Switch being such a JRPG powerhouse it to be expected.
Yeah, the HD era makes doing graphics a much more expensive and complicated undertaking so for many JRPG developers instead of going to home consoles they went to portable systems which over time developed graphics on par with previous generations. The Switch is poised to inherit those developers, especially since despite it having the power to do more in the current climate they do not necessarily have to.