a fireman who needs to learn that water puts out the fire?
So, you really are as dumb as your writing suggests...
Do you think water is the only aspect of putting out a fire? Do firemen have to train, learn more specialized skills, learn how to deal with increasingly difficult situations, and learn the many different kinds of fires and dangers they'll face?
Are you suggesting that they simply take a new fireman and just put him in the middle of a forest fire with some water and no training? Because, according to your simplistic analogy, a person should "just get it" without having to actually learn anything. If that is what you are saying, then you are not talking about development or learning at all.
Sexton is 19 years old, and he's already shown immense improvement. Based on the improvement we've already seen, I think it's fair to conclude that we should be patient and see if he KEEPS IMPROVING.
Does he need to improve his passing and playmaking? Yes, absolutely. But people who want to limit a 19 year old's ceiling after 30ish games of NBA level basketball are jumping to conclusions far too early. Do I think he's going to become the best playmaking PG ever? No, I don't think so, but I also think he could be above average if he decides to really prioritize it.
That said, I'm 100% fine with him prioritizing his scoring right now, especially with the dumpster fire rotation the coaches currently have around him. In fact, it's possible that the coaches are ENCOURAGING him to focus on his scoring first, in order to help him feel more comfortable with the speed of the NBA.
To make strong pronouncements about what he's capable of doing in the future seems premature to me. Especially when we've seen him improve greatly at every level, including the NBA.