The quality of the story is a matter of opinion, but the linearity of the story is objective fact. Just look at the chart you posted: there is one linear story to follow, with just occasional branches to alternate endings or splits that immediately merge back together.

Most VNs are structured as routes. The reader does not choose how the story will unfold, but rather chooses one of several linear stories to follow. I would classify that as a fundamentally linear story. The fact that the route is chosen by a choice in the middle is not really different from choosing the route from a menu at the start. In fact, most people use guides to get on the desired route.

SubaHibi is even more linear than that, because the playing order of the routes is enforced. Each route is unlocked only after the previous one is completed. There is one "True" ending, which is required to be completed last. The mysteries are only fully resolved by reaching the True ending.

(I don't think the True ending actually adds anything. In fact, all the mysteries were resolved to my satisfaction less than halfway through the story. But that's a matter of opinion once again.)

So it's linear if you ignore the parts that aren't? Without a walkthrough and a some meta experience with VNs it's pretty easy to end up somewhere other than one of the four true endings and walk away satisfied.

Anyway we aren't going to agree here. I am interested in two things: what VNs you do like... and what VNs you would consider non-linear. The discussion can't really continue without a point of comparison.

I am sincerely curious what you consider a non-linear VN. Maybe I've been unconsciously avoiding them so my perspective here is too skewed. Do you perhaps mean VNs where you choose where to go each day, e.g. さよならを教えて～comment te dire adieu～?