Theres a huge difference between picking your nose every now and then and farting 24/7. Wario being a bit gross was a small trait that only existed in some artwork and loves cracking gross jokes in a q&a, "Wario"ware took that small trait and stretched it out to ridiculous proportions.
The misconception that Wario was super gross in the jp version is also a gross exaggeration. The only differences between the west and jp portryals is the commercials. The west portrays Wario in a more sinister light while in the jp version hes portrayed as a goofy anti hero and rival to Mario. And the only examples of Wario being gross is a tiny fart joke in Wario Land 2's manual, a few poop stickers, and 6 questions revolving toilet humor in a q&a of 30 questions. His gross sense of humor was a small trait, all his other traits like his greed, his strenght, and egotistical nature eclipses that small trait.
There are major differences between Wario Land's and Warioware's portrayals of his character. Specifically his greed, strenght, weirdness, and grossness.
In Wario Land his greed pushed him into being a villain, to go on amazing treasure hunts, and participate in exciting sport events. In Warioware its used to make quick time, repetitive microgames involving ****posts and toilet humor.
In Wario Land he has Herculean strenght. He beats down hordes of monsters, piledrives enemies bigger than him, and works out routinely etc. Warioware threw all of that out the window and now he cant even lift up a golden toilet.
In Wario Land he has zany tranformations and hilarious expressions. The weirdness in Warioware are just random ****posts.
In Wario Land his grossness only existed in some artwork where he lazes around after a hard day of work and cracks a few gross jokes, Warioware butchered him into a lazy slob who sleeps all day, eats unhealthy snacks, and farts 24/7.
Wario was a well rounded and fleshed out character with plenty of well written traits in the Wario Land days. Warioware has NONE of the traits nor charm Wario Land had, hes nothing but a gross carciture. All Warioware did was stretch 2 small traits ( being gross and lazy ) to ridiculous proportions to the point where those are his only traits.
He doesn't lack this strength in Smash. He even gets far bigger hands to show it off.
The character is still motivated by greed, going after Trophies in the SSE. They still reference that in various Events.
Problem is, he can't do a lot of that stuff in Smash and be balanced, and still show off the other major Wario series. Both series are major and important to the character. He shows off both overall in different ways. Also, Wario was designed to intentionally look ugly and more gross, as well as some of his transformations are actually gross-like, like turning to a pile of sludge. His personality is still there, including in Smash.
He definitely has his egotistical nature. The personality you speak of, which is canon nonetheless, is closer to how it's done in WarioWare regardless. It's not inaccurate whatsoever regardless. People think it's exaggerated, but it's really not. It's just not focused on how he was less gross in Wario Land compared to WarioWare. It's still his official personality, just not from the game series some want. And there's nothing really wrong with that. So the liberties really just are moveset-based. Personality is still based upon his own series.
And that's what WarioWare does. It doesn't really go indepth into a lot of personality. That's the one that worked with mini-games. It doesn't really matter if it was "exaggerated" or not, it's still what they went with. It's fine for people to not like his updated personality. I get that. But that doesn't mean it's inaccurate for Smash, which is the point I'm making. Sakurai based him upon his WarioWare personality, not his Wario Land one. That's not a "liberty" at all. The moveset, sure. A lot of the moves are more based upon his exaggeration of his abilities, yes. Him growing his fists to attack and such really aren't that like Wario Land, but it does fit the more unique nature of WarioWare's crazy shenanigans. The motorcycle is obviously based upon that series too. He still has more than one move from Wario Land, as pointed above. But also like I pointed out above, you could easily split them among two movesets, which might be better for a lot of fans instead of using his WarioWare personality and unique moveset with a few Wario Land moves. Though to be fair, many characters are a combination of new and older(Link pretty much had his OOT self, but used items he couldn't in that form, including the Boomerang, while also taking notes from Zelda II with not just the Jumping, but the Downthrust and Upthrust).
It's possibly a case Sakurai isn't a fan of Wario Land and prefers WarioWare. It's still the same person who just moved onto mini-game corporations in his life. A different way to show off his greed. I mean, it's not like he can't do different things. Everybody changes. I get where you're coming from, but he's depicted as a specific but accurate version of Wario, which Nintendo went more with as his main personality in WarioWare overall. It's kind of his most prominent version these days too, so that could also be why he was chosen(another is to make him a separate series from Mario, as Wario Land isn't nearly as distinct in comparison. Though still highly distinct).