I have respect for your viewpoint, but it was becoming a problem in postwar London that was only going to increase greatly with the end of petrol rationing for cars, the steady increase in vans and lorries and the wishes of a lot of the population to visit green spaces outside the London County Council area, but within the range of 'red' bus services which provided hordes of extra buses and extended routes on Summer Sundays (sometimes Saturdays too) with a flexibility that was obviously impossible with a tram network. The centre-road-boarding was one of the reasons why the London Passenger Transport Board had elected to replace all trams with trolleybuses in the late 1930s, a process that was well underway before outbreak of the Second World War. Trolleybuses in London had pavement stops, as did buses of course, though they weren't often shared, I can remember, admittedly only vaguely as I was very young, the tram stops at Eltham Church and Lee Green, together with the terminus at the south side of Southwark Bridge (no further because of City of London intransigence) which all disappeared with the remaining tram routes in July 1952. It was certainly true that some roads did lend themselves better than others to tram tracks e.g. Blackfriars Road, the Victoria Embankment, Mile End Road, but many others (e.g. Brixton Road and Lewisham Way) didn't. After the war the transport authority had a rethink about trolleybuses and found the advantages outweighed by the disadvantages. I don't think allegations of short-sightedness can realistically be levelled at those authorities, unless their clairvoyance to concerns of the 21st Century is expected! It was the right decision at the time: now, whether more tube lines should have entered the mix as well is another matter entirely!
I respect your viewpoint as well, of course!
From where I stand though, the explosion in car traffic happened in all the major cities on the continent as well at more or less the same time. Those that were - at that time - considered progressive got rid of their trams with exactly the arguments that you bring. The slower ones kept them (not entirely of course, loads of tram routes in Vienna were closed, but the process was so slow that at some point, trams came back en vogue before everything closed). And we are very happy about it (mostly, some car drivers obviously still complain - contrary to what has been said here, roads are very often not broad enough to have separate lanes for cars and trams, so if you drive, you will regularly be held up by a tram at a station stop), even though in continental cities streets in general are not automatically wider than in the UK, so that has nothing to do with it.
The best example in Europe is Berlin. The West got rid of trams, the East didn’t and nobody would think to close them now (I admit though that Berlin generally has wide streets, but this is not typical for most continental cities).
Actually the same happened in regard to city motorways - those were, as everywhere, planned in Vienna as well. But as always, we were so slow in building them that a change in transport policy towards „the car is not everything“ came first and they were cancelled. As a result, we have very few motorways within the city borders and none of them reach the center. And we are - again, with the exception of some motorists, mostly those that commute from outside - very happy about it.
But enough said, I think. It doesn’t change a thing anyway, because those tram networks are gone and if you build new ones, obviously decision criteria and standards will be different.