Absolutely agree with this.
Charcoal trousers can work--with a light grey SC (which is hard to pull off in and of itself), or sometimes with sweaters. But yeah, they are not particularly versatile, are hard to do well, and I rarely wear mine for these reasons. And like you, I would not advise newbies to buy them. Mid grey, mid grey, mid grey, maybe some shade of brown.
Honestly, mine probably get worn the most when I do something dumb like mistakenly take all my mid-greys to the cleaners at the same time. Whoops.
DW's last post was more helpful than anything from the last few pages. I Hope we can move on from this.