I’m afraid that another reason there isn’t a need for advanced Wicca classes are people like me. The ones who practice in the style of Granny Weatherwax in the Discworld series by Terry Pratchett. The ones who are old enough to realize that intent, headology, style and practicality work better than any spellbook or course that can be bought or looked up on the internet. And you can’t teach that.
Practitioners like me know spells that work are not dependent on the right colour candle or the correct herb. That there is always a substitution that will work if your will is focused enough. That tools are extensions of your intent and you and not the other way around.
One of my favourite scenes in the Discworld books is Granny W using the wash tub for a cauldron and a kitchen tool for a wand. And Magrat , the new age apprentice not exactly knowing what to do about it. Nanny Ogg falls somewhere in between but mostly on the practical side just more pleasant about it.
We know that practice makes perfect and focus is always the practice and the point not objects. That most of the stuff people say you HAVE to have is bunk. Practice makes a magical practitioner not reading a book or taking a class or reading or even writing a blog. That knowing what the moon and sun and stars are doing is nice but not necessarily important. That just because it says use sage for the spell doesn’t mean that if you don’t have it you can’t substitute rosemary instead.
Thinking is the most important thing. Common sense is better than a grimoire. Things like being skyclad when it’s cold is stupid and better to wear clothes than catch pneumonia even if the calendar says it’s supposed to be spring. That maybe tying back your long flowing hair is a smart thing to do before you light the bonfire or candle if you want to keep it. Burning hair smells really bad and you do not need to be the ritual sacrifice. Sacrifice stupidity instead.
An open mind and heart and common sense are the best advanced Wicca classes.