I don't remember where I heard the exact quote, but I usually check out this channel, though do note he isn't a native English speaker and relies on text to speech.
Well based from others (needs more clarification); El, Spee King, Seiun and Special Week are called the "Strongest Generation" since they tend to meet in several races each other "compete" as if it was a battle royale.
The quote here is a reference to the old JRA commercials to commemorate certain horses and promote races.
This one actually came from El Condor Pasa's commercial. This one can have many meanings. Back when El Condor Pasa raced, she was not allowed to participate in pretty much any of the big races because she wasn't a Japanese born horse. Her father was American, and her mother Irish. She was japanese trained. She was born in the golden age era because there were so many horses that could win, the competition was so stiff, and none of the other horses would back down of a race just because the race had strong opponents. Everyone was willing to risk losing, to win. But she wasn't allowed to race against them, except in Japan Cup where international horses were allowed. In Japan Cup, she defeated all her japanese opponents, and then was pretty much forced to go overseas for international races. You guys know the rest of the story.
Many people believed El Condor Pasa to be the strongest among the generation, but many people also argued that "How can she be the strongest horse in japan when she didn't race in Japan?" I think the quote is making 2 statements. "We can't become stronger by ourselves." One meaning is that all 5 of the horses were able to become as strong as they were because of their fierce rivalry. The second meaning could be saying that, 'unless we get rid of these rules, we won't be strong enough to win on the world stage.' as commentary to El Condor Pasa's heartbreaking 2nd place at the L'arc.
The "Japanese born" horse rule was abolished a few years later.
