Something else worth noting about Dixie Kong's "lack of support" is that she is currently in a situation similar to Isabelle. Isabelle also did not have much support in fan polls,
as seen in this Source Gaming Smash Ultimate poll. Dixie Kong made the top 20 in that poll with 267 total votes, while Isabelle only received 30 total votes. In addition,
Source Gaming's Smash 4 Japanese poll also shows that Dixie Kong was a top 15 character choice, while Isabelle was no where to be seen. It's worth noting that Isabelle was an assist trophy in Smash 4, but other Smash 4 assist trophies like Waluigi and Shadow still made the list. Lastly,
r/smashbros also had an echo fighter poll not too long ago, and Dixie earned third place while Isabelle earned fourth place. With Isabelle eventually being added and becoming a semi-clone, it shows that Dixie Kong could also easily be added to Smash in a similar way. The fact that most people also thought that both Dixie and Isabelle would be echos, only for them to be proven wrong when Isabelle got her own spot on the roster, shows that some people may have underestimated their chances as fully realized characters.
Overall, my point is that Dixie Kong may have been overlooked for various reasons, same with Isabelle before her reveal. This could be anything from not being as heavily requested as other characters, King K. Rool having higher priority, or even Dixie Kong being dismissed as an echo by some people. I think it's shocking that Dixie did not make the initial roster, considering her importance to the DKC trilogy and Tropical Freeze, and I definitely think she deserves to be a semi-clone or unique character rather than an echo. With many highly requested characters like Isaac and Skull Kid out of the picture for now, Dixie Kong suddenly gets bumped up quite a few spots in terms of the most wanted, realizable characters for Ultimate.
If Nintendo wants to promote their own brand with a couple of DLC characters, Dixie Kong would be a great first-party choice for her importance to Nintendo history. It feels so weird that other reoccuring Nintendo characters like Peach, Zelda, and Samus are playable, but not Dixie Kong. Including her would make the roster feel much more complete, and with Tropical Freeze on the Switch, many potential consumers would notice her during Black Friday shopping and beyond. I think Dixie Kong would be a great DLC character choice, and she could come with a Tropical Freeze stage like Scorch N' Torch, as well as music from the Country trilogy, Returns, and Tropical Freeze. Regardless if she's added or not as DLC, she will remain my most supported first-party character, because she very much deserves to be playable and it's a crime that she's not already there.