Hadit is correct. They didn't 'go away', they just don't preach to the masses anymore. Look and you will find them. In larger covens there's a council of senior members who are there to teach and help the coven with smaller issues.
Do you mean people like Scott Cunningham, Aleister Crowley, Doreen Valiente, Gerald Gardner and so on? They died. They were the people who brought witchcraft to the masses [Cunningham was a second wave technically] but they died. There's still notable authors who do their best to guide new members, but its not as big for two reasons. One, the market is saturated with books on the subject, so there really isn't a 'one and only' like there was 50+ years ago. Second, Lark wrote a very interesting article on the subject of 'The Elders' where she made the point, they stopped helping everyone because the majority 'know everything' and the attitude has made them go away, letting you come to them. They aren't considered wise for nothing.
Personally, we have elders to speak to. Not naming names but I'm sure you can make your own list of people on this site who are very knowledgeable. They may not teach, but if you are stuck they will help. [Normally forums because they are busy but try messaging them] just be sure you've tried first. Asking 'The Elders' something like 'which element is associated with wealth' might be better for the all knowing elder Google.