
Goku's ability to copy and adapt to abilities is part of what makes him such an amazing character & martial artist
People always see Goku as just someone who's really capable of martial arts that knows an extreme amount of techniques, even considered a genius, but something that has been a valuable trait of his since early on (as early as Chapter 15 as I recall) is how he can overcome any obstacle.
He learned Kamehameha, which took Roshi the greatest martial artists in the world *by far* 50 years to create and master, when he was like 12 without any knowledge of ki. And throughout all the Budokai Tenkaichi tournaments, he's always overcome what he was capable of prior to going into a battle by learning his opponents moves or just copying it.
It's just such a cool ability that he has where he can learn anything combat related as long as he sees it himself.