The Great Central had less connectivity with other rail routes than just about any other comparable line in Britain. From Nottingham to Woodford there was nothing. About the only connectivity of consequence was with the Great Western at Banbury, via a spur. It actually carried very little freight traffic apart from some coal traffic from Nottingham/Sheffield down to Banbury, and a lesser amount continuing to London which after 1923 the LNER found convenient to keep it off the East Coast main line. This traffic ran down substantially in the 1960s as domestic and gasworks coal usage disappeared, and power stations in cities like London were replaced by ones where the coal was, in Yorkshire etc, with the end product, electricity, being transmitted rather than sending the coal down.
Every main point along the line (Nottingham, Loughborough, Leicester, Rugby)had a station separate, remote and unconnected from the much more used main station of the town (in passing, HS2 is poised to repeat this error). Rugby is probably the worst example on the old GC. As a result even the handful (and they were only a handful) of through expresses per day didn't carry a lot. The busiest train was generally the York to Swindon/Southampton, but that only ran once a day.
The local stopping trains on the line were normally so much empty stock, from the early loco/carriage days right through to the dmus at the end.
As far as the commercial value of building the line is concerned, let us not forget that the MS&L, who promoted it, was said by investors to stand for "Money Sunk & Lost", and the new GC name they gave themselves when the line opened was now "Gone Completely". And so it proved.