British Rail had one huge advantage. It was cheap. You didn't need to book weeks in advance to buy a seat without requiring an extra mortgage and there were few restrictions on ticket use.
It was, of course, starved of funds. Ironically, the present so-called private operation costs the taxpayer way more, in real terms, than BR ever did. And for that, we get an overpriced, unreliable and shit service.
I recently went to Reading, first class. (The benefit of being old I have a Railcard.) The seats were not much more comfortable than Metrolink, albeit there was more legroom. On the way back, people were standing even in first class. My reserved seat was lined up against a solid wall, so I had a choice between staring at the tiny sliver of window that belonged to the seat ahead or looking at the arse of the person standing next to me. No trolley service of course as it could not get through.
Absolutely diabolical. BR had its faults, but I never recall travelling in such discomfort, ever, in BR days.