Note that trash collectors call them selves sanitation engineers and stay-at-home parents are domestic engineers.
Which is exactly the point. This whole objection is dumb. Engineer is an English-language word and the attempts by professional societies to monopolize it and stop the general population from using it should be fought vigorously. If you want to require and imply a level of education and a set of standards, use a new trademarked term (like PE or Eur Ing or CEng).
"Doctor" is a reasonable comp: trying to remove that word from English and only let members of a certain cartel use it would be ludicrous, but the public interest is served by having a term that's reserved so that the public can have a baseline level of trust--hence MD (and DDS, RNA, DO, and all the rest).
There's no confusion here. Nobody thinks that a doctor of philosophy, a witch doctor, or Doctor John is a board-certified neurosurgeon any more than anyone thinks that an audio engineer, software engineer, or sanitation engineer is a certified civil engineer, and the word in English predates the narrow engineering-society sense by about 500 years.