The thing is, they aren't even trying it. Just look at the story mode, even to legacy characters, nothing in that story is relevant to anything. They don't even care about legacy characters.
They only make new characters based in the most stereotypical market by region research, then they choose a random martial art style for these characters and that's all. This is happening even since DOA5.
What's Mila personality?, being a Bass fangirl and really cheerful. That's all. She already meet Bass, so, what now?, most likely she will be like Hitomi since DOA5, a joke character that will only show to say a few random things and then she will lose.
Rig is Buzz Lightyear. Press button 1 for nice bro mode and press button 2 for mid boss mode. That's all.
What are his true emotions?, Internal fighting?. We know nothing about his past, not like they care or even have a idea about it.
Same with Marie Rose. Why is she so loyal to Helena?, how did they meet?. Literally zero backstory, you have to believe she was always there and she cares so much about Helena because why not.
Honoka the same stuff. Who is her mother?, It was her another Raidou victim?, what does Honoka know about her father?.
Team Ninja: who cares.
Nyotengu is a really fun one. Ryu defeats her and don't kill her because she is too kawaii to be evil. Then she just goes to have fun trolling Hitomi/Leifang/Brad/Eliot and in the end of the day she appears in DOA tournament, people felt in love with her not asking themselves what a tengu is and if she can be evil and well, who knows, maybe Nyotengu will be next Japan top idol.
Raidou, the fearsome final boss. Everyone fears his return, because he's so strong and he can do so many evil things, right?.
But then he dies before he can do a shit. You have me waiting almost two fuc*ing hours just for nothing. For a dude that just laugh a few times and then dies at the departure from the school.
Someone at Team Ninja thought that a final boss that accomplish literally nothing would be really popular.
Phase 4 ... oh boy, this one is the best one. Do you remember her personality and her cool sword at DOA5 story mode beginning?, because TN doesn't, not even Bayman.
From Donovan final weapon to just a Saibaman in mass production that ninjas can defeat as nothing.
Just great.