do you think it's possible to be very attractive and for a girl to not be interested?

Yes, of course. I think that it comes down to semantics as well. It's related to this :

do you think different girls have different types?

Yes, but I think that there are common denominators, in both men and women, that always increase your attractiveness.

I think it can be confusing actually due to the word "attraction". When I was younger, I was not attractive in general. I was needy, didn't have any self-esteem, lacked confidence, my social skills were not very good, etc. Some girls were still interested though, so I was attractive to them. So when I say that for a particular girl "I wasn't attractive enough", it doesn't mean I can do anything about it (I could, potentially, but that's the outcome bias fallacy), but my type just wasn't interesting for her. She just likes a different type of man.

To reiterate the point, of course girls can have different types, but I think that most men benefit from certain traits. So some girls like the business man type, others like the surfer, the rough player, etc. But it's quite possible that all of them are confident and secure men that have their passions and have no issues with their own sexuality and masculinity. Does that make sense?

what's more important knowing what red pill taught you about the nature of women OR being able to sense whether an individual girl likes you enough or not?

Let's say that if I had developed only the latter, the former would have come to be already. As I said in my first post, I got red pilled before the concept existed outside The Matrix (or when it wasn't so popular). I learned a lot about women by becoming more attractive and seeing sides of them that I thought didn't exist (both positive and negative).