This sort of thing is always going to be a personal thing really. I wouldn't call them going stale exactly, although you could levy that towards Pokemon more than anything else as there's a third Pokemon game in the span of just 12 months releasing soon.
I feel it's because most people are too afraid to try a different game outside of their comfort zone, outside of their usual franchises, or isn't putting the effort in; lets face it, when it comes to Nintendo, the only franchises people tend to talk about the most often is Mario, Zelda and Pokemon, nothing or not much else outside of those. There's so much variety of different types of games these days from Nintendo, it's crazy how ignored some are; remember when poeple said there's no games on the Switch? Now there's a lot and suddenly people are self-limiting themselves and claiming they're not interested in anything, while still sticking to the usual stuff.
I'm trying anything and everything out, as long as they're solid, having not played previous titles before, like Xenoblade, which by that token, there's too many games to keep up with; only finished Fire Emblem Warriors: Three Hopes literally the night before Xenoblade 3 came out, which I'm trying piling more time on each day before Splatoon 3 comes out.
So really, staleness is very subjective and dependent on one's personal tastes; if you didn't like those, that's fine, because at least you tried it instead of writing it off. Although that said, I'm holding off on Pokemon Scarlet and Violet to see how that pans out before I take the plunge; still burnt out from it, we only had Legends: Arceus earlier this year and focusing on Bayonetta 3.