Yeah she's spot on. The show works so well precisely because it venerates the source material so much. And indeed, you don't need to have read the novel to sense the underlying structure.

As for the the LGBQ and Black people representation, this is the one of those shows that works it into the characters and themes without any of it feeling forced and pandering. It's an integral part of the plot, using the realities of that time and at no point does it feel like representation boxes are merely being checked. Though to be fair I suppose this is easier to do in a historical drama where the attitudes inherent to the period create natural problems for a story to coalesce around.