I’ve played Tekken 7 recently and I love the series, just like I loved it when I played Tekken 3.
That said, story wise and Tekken 8, I don’t think you’re supposed to root for any of the Mishima family. Heihachi did horrible things, Kazuya did horrible things and Jin became Putin in Tekken 6. They’re anti-heroes.
It’s kinda like Breaking Bad or Rick Sanchez from Rick and Morty. You’re not supposed to wish they succeed.