Making it on experience and being only a little short isn't more impressive than taking the time to get it right by having someone teach you what you don't know.
Keep in mind that the most likely reason by far that they don't have decent instructors is because they're dickheads. Kid is another conqueror but not the type who makes allies (an ability Mihawk, the third mentor, noted as the most dangerous). He came across Shanks and Rayleigh, like Luffy, but apparently didn't inspire any goodwill. He'd never humble himself to ask for help or anything. He's basically on track to become another pirate who only becomes a key figure around the age of like 40.
in this fight I will say that using the force of magnetism to crush Kaido is actually a pretty good idea. But it's all they have and it wouldn't be worth shit if it was Kid and Killer vs Kaido round 2. Hopeless fafafa