I'm not sure who thinks that Sighthill Industrial Estate is easy to get to, unless you happen to live close to the Calder Road and are happy to walk in all weathers. There are buses past one end of it, and trams past the other, but no public transport that passes close to Thomas Thomson House. Also, there is already a shortage of parking in the industrial estate, and trying to get out of it in the rush hour is a nightmare.
Who says that GRH isn't fit for purpose? It is superbly fit for use by the public. It's a magnificent and impressive setting for the search rooms, conveniently sited for locals and visitors to access by bus, tram or train.
The genealogical aids on the internet are just the very tip of the iceberg. There are literally tons of documents available in the National Records over and above the BMDs on the Scotland's People web site.