GD Dmitri would have been a great match, but yes, too wordly for the Empress, and beyond the understanding of her sheltered daughters.
According to Olga's English wikipage:
....In 1913, Duchess Marie of Mecklenburg-Schwerin asked Alexandra about a potential marriage between the 18-year-old Olga and her own 38-year-old son, Grand Duke Boris Vladimirovich of Russia. Alexandra was horrified, because "the idea of Boris is too unsympathetic." She refused to allow "a pure, fresh girl" to marry "a well-used, half worn out, blasÚ young man" and "live in a house in which many a woman has shared his life."....
This was because GD Marie had BIG ambitions. She felt she was a far better candidate as empress than Alix but that was never going to happen... but with Alexei's illness, the removal of GD Michael from the succession, her boys were next, and so why not push for a match with one of the Tsar's daughters? That would give a potential succession even more legitimacy.
The Vladimirovichi were, and still are, rather deluded. They haven't changed (see Mrs. Hohenzollern and her son The Generalissimo).