It’s probably much the same as with any skill, like driving for example. Of course everyone can learn to drive a car. But it can be a difficult slow progress for some even if it is very fast and easy for others.
Compare someone who has trained 2 years and constantly failed to take his/her’s driver’s licence to someone like Michael Schumacher or Mika Häkkinen.
On the other hand suppose that someone who hasn’t heard about LD:ing is a natural that just doesn’t know about it yet - then it would be a shame to scare him/her away. It’s of course impossible to tell before he/she has tried how hard/easy it is going to be. I would also focus on the good stuff and everything i find cool about it if i was writing a newbie guide. But i would not over-exaggerate how easy it is to do, because that remains to be found out for each individual dreamer.
What placebo effect? I was half sure LD:ing wasn’t possible (fake) when i first tried it. I found out i was wrong by having one and it took me less than a week