There are certainly thoughtforms that have been created by people who didn't understand the magic and approached it in the same way you'd approach the goetia.
The gods themselves are most certainly real entities, just as tad challenging to reach if you don't know what you're doing.
Lovecraft was a mix of fiction and visits from these gods. Nyarlathotep crops up alot in many different paths. Many people believe that he was even mistakenly evoked by Crowley who mistook him for another spirit.
My advice would be to never dismiss magic in media as complete fiction. You'll be surprised how often magic in media has a base in reality.