George and Philip, I often wonder what this disagreement is actually about.
George says, "As a practical mode of transport they had outlived their welcome". That's a statement of fact, no disagreement. They no longer exist as a "practical mode of transport" and have not done so for decades, except in one or two special industrial cases (the SAPPI-SAICCOR paper mill in South Africa, where they finally stopped last year, and the coal industry in China, where a handful of steam locos are still clinging on as diesels rapidly take over). Clearly they are never going to return as a "practical mode of transport".
On the other hand, Philip says, "most people who ride steam trains don't find it unpleasant". Note the tense - "ride" (present tense), not "rode" (past tense). And George agrees when he says, "As toys on preserved lines, where people aren't forced to use them, perhaps they have an entertainment value". Precisely - that is the only way people can ride steam trains these days, and most people who do so enjoy the experience, so there is little point in harking back to the days when they were the normal mode of transport. Yes, "Most people were glad to see the back of them" as a normal mode of transport, but several decades later (ie now) most people are quite pleased to see the handful of preserved ones whether as toys, or entertainment, or working historical artefacts, or as an incredibly important reminder of our industrial heritage which helped to create society as we know it.
As to obsessing about the past, the word "obsessing" is pejorative and value-laden, but basically it's what historians do. It's why people are interested in vintage cars, old aeroplanes, old ships, old postage stamps, old books, old military uniforms, old weapons, old medals, dinosaurs, English stately homes, palaces, antique furniture, agricultural machinery (I know a bloke in South Africa who has 400 old tractors), re-enacting old battles, making TV programmes where celebrities live in a Bronze Age village, etc. It's why we have museums. It's part of educating ourselves about the past and how it led to the present. It's also entertainment. It's why people visit the Tower of London, or Hadrian's Wall, or the Somme battlefield, or ancient cities like Rome... or ride on steam trains.