This feels like kind of a weird take to be having...or rather, it feels like the OP has been a little too fixated on those particular personalities and just...hasn't been paying attention to the personality the rest of the company's been showing? How do you claim the executives are boring when Nintendo presentations contain the likes of Koizumi channeling cosmic powers and simulating frozen tundras during the Switch reveal, the same man transforming from normal suit into red Mario garb complete with Cappy to debut Mario Odyssey, Nogami going on stage making numeric poses and pioneering the sunglasses-clad scientist motif of the Squid Research Lab that has remained the core of that series' marketing, Yabuki rocking hoodies with the double thumbs-up and striking a pose while bodying the winner of the ARMS invitational tournament, and...like literally everything Sakurai does or says during his Smash showcases? Doug Bowser hasn't had a ton of public appearances yet but has already been featured interacting with and shooing away a CGI Bowser Koopa. For years now Nintendo hasn't really done big live-stage events and the Nintendo Directs have continued to become more focused in how they convey information, so there's less of a need for big live public demonstrations, but even so I think Nintendo's employees have continued to show a ton of personality.
There is no person that completely fills the role of Miyamoto, or completely replaces Reggie, but they don't need that in order to still be fun, and more importantly, to convey the quality of their games.