Tsukihime and all those type moon stuff is too dense to play off of a minor thing such as someone else telling you to do so. You need a lot of self-generated motivation to dive into those things.
I come from the fighting game side of things so I have known melty blood for over a decade now but I had no interest in the series at all but a year ago I got into fate due to Saber being a guest char in a game I got (nitro+ blasterz) so I figured I might as well check out Tsukihime too since the worlds are somewhat connected.
Point being, without that kind of drive and motivation, people will lose interest way before the story gets good.
Now, on the matter of Shiki being a good main char or not, he's a little bland early on and I only really liked him in one or two paths. He was more of a vessel through which the heroines shine, and good at that, but not that great otherwise.
