I quit smoking years ago by using a vaporizer and quickly learned to mix my own liquid in order to lower costs, keep track of what was in it, and get lower nicotine than what was available in most commercial stuff at the time.
Not claiming it's as healthy as breathing fresh mountain air, but it's hardly some innately toxic "witches brew" of unknown compounds. Made a huge difference in my health and I haven't smoked in 7 or 8 years now. Sadly, despite the lengths many reputable producers of vape liquid went to regarding ingredients and preparation, many have been put out of business by harsher restrictions than those on actual smoking tobacco.
This is about the only known-to-be-true statement in that paragraph.
Pure nicotine is dangerous, and I see someone else has discussed the "witches brew".