As others have said awhile back, advances in development made the genre obsolete, as ridiculous the analogy may sound, but it's kinda like if they tried making pong today, it wouldnt work. On top of this the popularity of the genre just died, it wasnt just Star Fox that lost it, but practically every game that was part of it, there was a minor comeback when the Wii was the thing, but that only lasted for so long that it died off completely afterwards, and Sin & Punishment died because of it. To put it simple Star Fox could've made a comeback had it come out for the Wii as originally planned, but they screwed that up, they even refused to show its face until now if anyone remembers some people asking why the series wasnt in Nintendo Land.
Though some developers do make em, the issue is that, and I base this on wiki dare I say, only special enthusiasts can make em, plus the audience is niche as hell, this is even applied to vertical and horizontal shooters, which are more poplar than it but are also as dead.
That's why i've said Assault was the perfection of the series, which is why I wanted a sequel of that game to get rid of Command as others wanted, hell i'd like to see a remastering of Adventures after what I learned about what happened during development.