I dont know if its something you are doing wrong, but my exp has been the same as everyone else on here. I have always gotten an email back within that day about meeting and they have always been accessible. Yeah, dont just walk to a professors class if they dont have office hours without emailing, but I feel like that is common sense. Some might be cool with that, some wont. But you are not giving the professors here enough credit.
Yeah... not sure how I could be doing something "wrong." Like I said, I never take more than a few minutes asking a question and I always try to email ahead to set up a time (unless the professor just doesn't email me back, which has happened fairly often). I'm glad no one else has experienced this though; however, it does make me wonder if just no one else is speaking up about bad experiences. I mean, this has happened on more than one occasion and with different professors. By far my worst experience was when I asked a professor a question during office hours, he rolled his eyes, did a big sigh and literally told me he wouldn't answer the question because it was something I should be able to figure out on my own. For what it's worth, I then went and asked someone else in the class - they didn't know the answer. Then I asked a friend who worked in this particular industry before school, and he too did not know the answer. So yeah, that left a pretty bad taste in my mouth.
With all that said, I have found the level of teaching quality to be top notch. Even the professors who everyone rags on, I find to be fairly decent. I should also note that I have had some very positive out-of-class experiences with some professors (Robinson, Balnave is super nice, Setear always talks to me at the gym even though I have never taken a class with him).