I do know those rumours but tbh I'm more willing to blame Nintendo for the failure of that game than Retro themselves - especially considering how controlling Nintendo tends to be with their developers.
I can't see how the people who revolutionised Metroid and arguably bested Rare in the 2D platformer space could seemingly fail so badly on their own that
years of work had to go down the drain. I can see an otherwise talented developer finding themselves in a lose-lose situation where their pre-existing management problems mixed in with a lack of support from higher-ups and roadblocks caused by "not fitting with Nintendo's vision."
Like, when you put it into perspective; Nintendo has only put out
two* new in-house, non-casual, major IPs in the past
20 years - ARMS and Splatoon**. It must have been an
incredibly difficult task trying to make another one - especially when Retro was probably not wanting to make a game akin to ARMS and Splatoon (i.e. multiplayer-focused cartoon-styled titles with lots of franchise potential).
*Arguably Xenoblade as well, but I'm not classing a franchise that wasn't originally meant to even see a world-wide release as "major."
**I'd also add here that ARMs is probably a dead franchise, and Splatoon is only at 3 entries and is already in the "yeah this probably needs a bit of a shakeup," phase for me lol
Eh, I think your take on Sony's IPs is kinda 'Nintendo fanboyish' lol, but I'll leave it there since you do have a point all around
Sony's IPs tend to be based on specific stories and, as such, they kind of have a 'shelf-life' Meanwhile all of Nintendo's IPs can potentially go on forever - and they, generally, have gameplay experiences that can't be found elsewhere.
However I do think that this represents a failure on Nintendo's part - whether it be a failure to create natural growth, or a failure in vision from higher-ups. For a company as large as them it shouldn't be an 'either or' whether an incredibly talented dev like NLG can make a creative, unique new IP or... Mario Strikers 3. There should be enough resources and support there to balance them out - especially since the individual titles very likely don't have the same budgets as a Last of Us or Horizon Zero Dawn does (this ain't a dig on those titles but, I mean, come on lol).
I don't know - I do want to see more titles released in Nintendo's franchises, but I don't want to see an overall lack of creativity where every generation is just an assorted selection of takes on the same small IP pool. They can do differently - as pretty much the entirety of their pre-Wii years shows - they're just... not doing that. It's working financially, for sure, but it's also not the most exciting thing in the world for me.