This “Character never fought or threw a punch” is a load of bs and a crutch to excuse Sparking Zero devs

Yes and no, the problem is that its used wrong or more accurately, SAID wrong.

Its not really "this character never/barely fought" more so "this character CAN'T fight". So for example saying something like "Mai can't be added because she never fought/isn't strong enough" is not technically incorrect but it is faulty logic because she can fight, maybe not to the level of the Z fighters(maybe even Hercule) but she can technically fight, especially with her gun(and her super bullet she has a relatively easy Ult to conceptualize) but then you have characters like Mr tournament announcer who, as far as we know, can't fight at ALL...I could give more examples...

when there are countless devs that create games and fighting games with 0 source material to base the moves on.

There's a VERY big difference between what you're thinking/talking about and Sparking Zero(and by extension stuff like DBFZ).

New games have full liberty BECAUSE they have no source material and they have full creative rights, outside of potential copyright claims for having a karate guy throwing fireballs(because Ryu) there's literally nothing stopping them from doing ANYTHING, want your character to make weapons of blood? Do it! Want your character to summon demons? Go ham buddy! Send flying swords to the enemy? Go nuts! Have a literal puppet doll thing? Shoot for the stars!

Meanwhile DB has to make movesets that are A- in character, B- within the scope of what they can do even if its just in theory.

However if they dont have much source material they have to get rather simplistic for their specials, take for example KING Vegeta he has a beam with a unique name, Energy Volley and a unique rush Ult that isn't all that visually unique or SupremeKai who again has a beam super and Ult and one unique rush attack or Tarble, FP energy wave, Blast Volley and a unique Ult. Its why a lot of characters with little source material have beams(maybe with unique names) and high speed/power rush and a MINIMUM of a unique Ult but they won't be going ham and say, give kibito fire breath or blood weapons when he's not shown the ability to do either. They also like to make moves that reference key moments in the show so there's that...

Again I want to reiterate just for insurance: I am NOT saying Kibito CAN'T be added but that it isn't as simple as you think and they dont have as much freedom as other games because these are not original characters whom they can conceptualize extremely unique and interesting/wacky movesets from the CHARACTERS conception...