Is this not the right way to think about it?

Well, obviously, you say it's not working for you so, no it's not. Yes, the more time you spend getting to know someone as a friend, the greater the odds are that that is all you ever be. Of course, there are times when two platonic friends become mutually interested in each other and start dating, but that's not something you can plan for in advance.

But really, I think you're making this a bit more complicated that it actually is. First, you need to accept that everything in life isn't simple and easy. It's like you're trying to skip the "getting to know each other" phase of dating, because you don't want to risk asking a girl out, having her say yes, and then you go out and find out that you're not compatible or that there's no spark, and then you have to try again with some other woman. You want to just go right to the part where you're in a relationship with a woman that you already know and like. So that's why you have this strategy of spending a long time seeing if you're really good friends first. But the truth is, you really can't know how well it's going to go dating someone until you actually try dating them. It is a different dynamic than being friends. Getting to know someone as a friend is not the same as getting to know someone as a potential mate. You can be great friends with someone and still just not work as a couple. So being friends beforehand is no guarantee.