Everyone is different, to look at everything so one dimensionally to say all humans work better together is a misnomer, a lot of humans work better when they are alone, there are pros and cons to working alone and working together. Albeit working together is more beneficial, that isn't to say it's absolute rule that all humans must work together, some people are so fast paced by themselves that having to rely on others just brings them down, for most people they work alone not because they want to but because others are not as fast paced as them or they don't share their dream. Imo it works hand in hand, you have to work alone first THEN you work together with others at least from an entreprenual stance.
Naruto is incredibly strong due to creating bonds with others and sasuke became strong by working with others, people say he worked alone but for the most part he hasn't really. I can't say for sure if Naruto is the strongest as there are many instances in Naruto when another character clearly looks stronger than another but the "stronger" character loses. Like against pein, pein manhandled Jiraya, you wouldn't even think Naruto oils even have that huge if a chance, however he managed to do pretty decently despite being at a huge disadvantage in sage mode. Sasuke and itachi evenmanaged to subdue DSM kabuto despite the latter being physically leauges above them. Looks can be deceiving but there is no doubt of Naruto being Demi god level, the only one that can best naruto is the coolest guy himself
