I don't think Nintendo knows how to make StarFox. They haven't been able to actually make a successful improvement to the formula since it was first released. StarFox 2 actually could have been that successful iteration, but they canned it for StarFox64, which is a remake of Starfox. Starfox Adventure pissed off everyone because it shouldn't have been a starfox game, Starfox assault did not do well for a multitude of reasons, Starfox command was fun, but shat all over any semblance of a story the universe had and didn't scratch the itch people were desperate for, Starfox zero was a half assed expansion to a tech demo that had a terrible gimmick the producer was married to but nobody wanted and made no sense (I can't focus on both screens at once), and they've basically called the time of death at this point.
Rail shooters aren't exactly knock out hits anymore.
Which is why I suggested multiplayer being a reason to bring the game back. A 4-on-4 or 5-on-5 Starfox multiplayer would be absolutely incredible on modern consoles.
The other reason Starfox is hard to do is because the game itself is quite short - IIRC Starfox64 could be completed in less than an hour - it was only 7 stages at most, 6 at least. Crazy short. Make the whole campaign 20+ missions with longer stages, totally possible with today's tech.
Rail shooters aren't exactly knock out hits anymore.