you're asking socially awkward + nervous + scared guys to 1. go out of their comfort zone and smoothly create inorganically an opportunity to strike up a conversation with someone, and 2. sprinkle in something that is considered flirtatious but not too strong that it falls under the category of "hitting on"
Now why these social cues are so often subtle or ambiguous is itself an interesting question. It's not one I have any good answers to though. In this area, as in most, I'm a phenomenologist and not a theorist. Needless to say the phenomenology I've developed precludes telling a woman I'm interested in about the phenomenology I've developed. Except of course when I think she might find it attractive. Human social interactions are marvelously complex. Frankly my inclination to start navel gazing has set me back once or twice.
BTW, I’m not talking about PUA stuff here. Rather, I would think of it as practising the art of conversation, and cultivating a curiousness about other people.
A skill that you need to practice with dedication and that "takes time" to learn still doesn't sound basic.
As someone that has participated in lots of flirting, conversation, and curiousness about other people, I can say confidently that being curious and being good at conversation are not sufficient to navigate flirtatious behavior successfully, unless you're using "art of conversation" as a huge umbrella term which includes charisma / etc. If you are doing that, then I'll note that probably the majority of people on Earth have not mastered the art of conversation (or even cultivated it much) by such a broad definition.