that's the thing tho; if you judge Wario from his franchise (both of them, even!) there's no relation to Mario at all. Wario doesn't depend on Mario to be a good character.
I'm not saying Wario needs Mario to be a good character. I never said that. What I'm saying is that even when Wario's own franchises (the ones that had nothing to do with Mario) were big and prominent, he was STILL there in Mario games playing the same roles he does now.
I think that what you say just proves that Wario has been reduced to a poopy filler character, and it's certainly not because his franchise flopped, like others Nintendo has been show to exploit by title alone.
Nothing has changed except Wario doesn't have as many of his own games. He's always been in the Party, Kart, and Sports titles.
It's weird really and I'm not blaming the fans, but it says a lot that Nintendo has completely sold us this image that Wario is just a bad Mario and we believe it, because they don't advertise his franchise enough, when it's good enough to deserve that both by sales and by virtue of their quality.
Wario was always "bad Mario" to some extent. That's what his name means! Even during the days Wario Land and WarioWare were prominent, there were games where Wario and Mario were rivals.
Get this. The year that WarioWare Inc. came out was the same year Mario Kart Double Dash and Mario Party 5 came out. It shows that while Wario had games that were completely divorced from the Mario series he was still starring in just as many Mario games.
You seem to be under the assumption that while Wario was starring in Wario Land and WarioWare games he did not appear in any Mario games. That's not true. He was. He always was.
It's true that WarioWare and Wario Land games have nothing to do with Mario, that doesn't mean his ties to Mario aren't strong outside of those games.
In short, while Wario own games have nothing to do with Mario, he has always been a part of the Mario cast. Meanwhile, the young tie wearing DK of Donkey Kong Country had a whole console generation of games where he never appeared in a Mario game. He finally did years later in Mario Kart 64 but his series had 5 games before that.