Plenty of historic trains stations have adapted with modern technology and the addition of new services. Admittedly, Union has a space issue that might (and likely would) limit its potential.
As for Ottawa being a mid-sized backwater, that is due to a lack of vision. No leader other than Laurier (guy who inherited a rough and tumble lumber town and did his best with the time he had, establishing the ancestor of the NCC and approving grand projects like the Château Laurier and Union), Borden (guy who's ambitions for the capital we're stopped by WWI) and McKenzie-King (guy who's ambitions for the capital we're slowed down by WWII, and largely based on the automobile which set-us back in many ways) ever had a vision for Ottawa. Even Jim Watson, arguably the most transformative Mayor in Ottawa's history, Ottawa's Drapeau, literally modeled the ambition of the O-Train to a Chevrolet, not a Cadillac.