I've explained this to numerous people over the last few days. That whole phrase is a matter of people acting like TMZ: taking something someone actually said, then omitting or adding words into something completely different. Just like they did with Battle of Gods.
1) What people THINK was said about Battle of Gods: "Akira Toriyama wrote Battle of Gods" What was actually SAID about Battle of Gods: "Akira Toriyama was heavily involved in the script writing process for Battle of Gods."
2) What people THINK was said about SSJ2/SSJ3: "None of the Saiyans use/can go SSJ2/SSJ3 anymore." What was actually SAID about SSJ2/SSJ3: "Super Saiyan 2 and 3 are nothing more than powered-up variations of Super Saiyan. After the fight with Beerus, Goku realized that mastering his normal state and Super Saiyan would raise his level more and sap less strength, so I think he probably won't become a Super Saiyan 2 or 3 anymore."
The part about SSJ2 and SSJ3 actually fits with GT, as Goku, more often than not, only used his base and SSJ form. Before he obtained SSJ4, he only opted to use SSJ3 when he had no alternative. Even in the Cell Saga Goku realized how burdening the extra SSJ levels were (hence why he had Gohan and himself 'master the original SSJ state), and it was more apparent by the Boo Saga. Goku doesn't like going beyond Super Saiyan, because it tires him out. SSJ4 doesn't burden his body like the SSJ2 or SSJ3 do, so Toriyama's statement is actually backed up by GT. There is never any mention that any of the other saiyans won't use the other forms. Only Goku. And even at that, Goku would likely use the forms in a pinch if he had to
well, i'm impressed by the greatness of your knowledge. i'ts not that i don't know such information, it's is just that being said by the creator, i have a tendency to take it as true. now, just so i can explain myself, what toriyama stated goes beyond what you actually said, first, in kami to kami, vegeta was said to have surpassed goku when fighting bills, it seems understandable, as he actually beat him up for good, what i actually felt to be weird is: he was at his first super form, it was really weird to be though before toriyama explaining such thing, also, goku also put up a good fight against a 70% released most powerful being of all "this" universe, he was also at his first super form, though he stood no chance at first in his third super saiyan. the fact that toriyama has explored the powering up of the original super form is also something i know, it was what made the recent statement have any sense to me. anyway, though i wrote such text, fact is that i only had some curiosity, it is not as if doujinshi should take up the originals as absolute, i will keep liking your work either way.