Cross country routes are local trains masquerading as long distance, thus with ridiculous prices and the requirement to do split tickets. There’s nowhere near enough capacity on the line.
Penzance to Exeter takes 3 hours - half the speed of a drive. From Exeter to Birmingham it’s another 2h30 at just 60mph average.
A good line would be an hour faster on both legs.
We also don't really have any of the major cities I meant in that context, Bristol I suppose. How do you get from Bournemouth to Bristol for example - via Dorchester with a station change? How about Southampton to Exeter - via Bristol? It's by no means the worst region, and I claimed the opposite, but it still suffers in the same way (albeit on a smaller scale) really, NW-SE rather than W-E in the North, in both cases its opposing the 'spokes' into London.