I've just finished an access (to law) diploma, and i'll be starting an llb in October. so, I haven't experienced it yet, but, I imagine i'll also find the material and amount of reading boring and pointless to wade through.
speaking generally, the way your mind is attuned must affect suitability to study law. I would imagine technical, deductive thinkers, like maths-inclined people, would do well. as for me, I prefer broad generalities, and abstract thinking. details I mostly think are pointless, and in any case boring.
but i'm studying law because I am an idealist, and I have an idealistic end for which being a lawyer is the means. so for me, that has been, so far, and hopefully will remain, enough motivation to do the work, and do it well enough to get good grades. on the same token, why did you choose to study law?
as for other subjects being more interesting, and the gdl being a better option, I imagine that's true for most people. there are a few subjects I am interested in, but I would despise studying them academically. philosophy rendered academic sucks all the magic out. I had a look at past Oxbridge exam papers, and, jesus Christ, I will say no more. which leads into my conclusion, that i am not intrinsically interested in studying anything at university, least of all law, given that 1 - I prefer to think with no artificial boundaries or constraints, as are imposed by academia, and only about things which are innately worthwhile (to me), and 2 - law is not something I am naturally suited to, being the 'opposite' kind of thinker. but, I have a reason to do it, so whilst I agree with everything you say about how boring law is, and anticipate i'll find it to be the same, it's also my only option, if I am to qualify, which is to say I can only tolerate study rendered through academia because of my end goal, and law is the first step towards it.