I think that, for the majority of students, your advisor's advice is correct. You need to focus on a particular problem, otherwise you won't solve it, and you can't expect to learn everything from text-books in advance, since trying to do so will lead you to being bogged down in books forever.
I think that Paul Siegel's suggestion is sensible. If you enjoy reading about different parts of math, then build in some time to your schedule for doing this. Especially if you feel that your work on your thesis problem is going nowhere, it can be good to take a break, and putting your problem aside to do some general reading is one way of doing that.
But one thing to bear in mind is that (despite the way it may appear) most problems are not solved by having mastery of a big machine that is then applied to the problem at hand. Rather, they typically reduce to concrete questions in linear algebra, calculus, or combinatorics. One part of the difficulty in solving a problem is finding this kind of reduction (this is where machines can sometimes be useful), so that the problem turns into something you can really solve. This usually takes time, not time reading texts, but time bashing your head against the question. One reason I mention this is that you probably
have more knowledge of the math you will need to solve your question than you think; the difficulty is figuring out how to apply that knowledge, which is something that comes with practice. (Ben Webster's advice along these lines is very good.)
One other thing: reading papers in the same field as your problem, as a clue to techniques for solving your problem, is often a good thing to do, and may be a compromise between working solely on your problem and reading for general knowledge.
Best Answer
I would suggest to talk to your advisor. Just tell him exactly what your are telling us:
you think that your thesis problem is not meaningful nor interesting and too technical.
If he displays as an answer some kind of rude behavior, then I think that it's better to change from subject (and from advisor). But my feeling is that you can have a constructive discussion with him. He must first understand what you don't like in your subject. Then he may propose a less technical question or a different angle of attack on the problem. He may explain the relevance of some technics that may appear boring at first sight, but that you will find both enjoyable and powerful as soon as you master it. Just as many mathematical courses don't reveal all their depth in the first sessions, there may be many wonders that await you in the next years of your phd. But some tedious work may be in order before reaching that point.