There's a real world out there where our children will be confronted with drug use and the promiscuity which it brings with it, and your "moral theology explanations" will answer nothing to them and be like water off a duck to them, as they are to me
Yeah, drugs have been around for decades. Moral theologists have written about alcohol, drugs, etc for CENTURIES. If one understands the principles then you apply them to your daily life. It's not that hard.
1) does the use of x thing cause the loss of reason? If yes, then it's a mortal sin, so you can't do it.
Exception: If there is a grave reason (medical or otherwise, then one it might be ok)...i.e. morphine can be used post surgery.
2) if the x thing doesn't cause loss of reason but does impair your reason slightly, can you do it? If you have a legitimate reason to do so, yes. If no reason, then it is probably a venial sin.
3) if the x thing doesn't impair your reason but simply relaxes you or gives you a "buzz" can you do it? If occasionally and it doesn't affect your duties of life, yes. If it becomes a bad habit, this is based on your conscience, because it could lead to bigger sins.
This is how one applies moral theology to one's daily life. If you're the type of person who can't deal with such analysis, and you need a "yes or no" answer to everything, then moral theology isn't for you. But you should have the humility to admit such and stop trying to force everyone to view the world through your eyes. God gave us all different temperaments, skills and thinking for a reason - life isn't "one size fits all"; that also applies to Catholicism, to some degree. No 2 saints are alike.