CFA questions

Are the sample questions from CFAI website (Candidate Resources Toolkit) useless? I don’t like that there’s no explanation given–just answers. Also, I remember someone on this forum saying they’re not good. Lastly, Schweser Secret Sauce says that these questions are not good because they’re easier than actual exam questions–but then again, they say that their exams are easier than actual exam questions and many people say they’re harder. Worth spending time on?