Goku's exceptionalism goes beyond just his attitude. You really think there were no good Saiyans to
ever exist but him?
What about the Super Saiyan God? What about the Saiyans who tried to resist Frieza and were killed off? What about the Saiyans who didn't want to kill the Tuffles? Unless the Saiyans are a hivemind, it's incredulous to believe there would
never be a Saiyan that would exhibit
some variance from the common cruel warrior type.
There have been numerous exceptions to the common denominator of Saiyan cruelty. Goku being "kind" is simply one aspect of his altogether unique characteristics. Bardock, Gine, Broly, Tarble and every other Saiyan who doesn't carry a homicidal itch are not just Goku. The series is more than large enough to accommodate some nuance in the Saiyan race.
It was canon until it wasn't. Toriyama even referenced it in his own manga before backtracking decades later. And he never evolved past being a normal saiyan in the special, unless you mean the dub version. That's what made it work; his psychic powers accomplish nothing, he only tries to stop freeza because he knows freeza will destroy planet Vegeta, not because Freeza was a tyrant or anything. Bardock liked his job lol. Bardock dies having accomplished nothing, and is forgotten. That's what makes the story work.
I'm just gonna leave this video here
That's some guy's review. Okay. I don't see what that is proving. I'm glad he likes it? The special's not bad but.... That's not the direction of the story based on the manga and what Toriyama wrote. It's a gaiden that flies in the face of the actual story. It's cool in its
own right, but it's not something exceptional that's being erased via giving Bardock an actual backstory in line with the story. It's like how fans were mad Broly wasn't just a blood guzzling roided monster in
Super, even though it gave him 100% more characterization and nuance than what Toei stamped him with.
Toriyama referenced that special because the anime
referenced his design in constructing his backstory during the Frieza saga. That doesn't make Toei suddenly mind meld their special into Toriyama's actual story. Your point about Bardock "accomplishing" anything easily applies to
Dragon Ball Super Broly, where he didn't overcome or save Planet Vegeta there either.
Not really seeing this dramatic shift in Bardock's actual story aside from scraping a Toei tv special and simply taking him in a direction that's different, albeit very similar to the previous one. Except sans the psychic impetus and torment. Hell, Bardock was questioning Frieza and the role Saiyans were playing in his empire before the visions. So what's with this whole rewrite of Bardock being a total monster?
He never was.