You are comparing football leagues in the 60s with current teams. That's a big mistake. Brazilian clubs were among the best in the world during that time. And, moreover, European leagues were not as good as they are today (there was much less money at the time). So your mistake as with many others is to think that playing in Santos was worse than playing for Barcelona or PSG. That's not the case, Santos was as good or better than any team in Europe.