Great cities need infrastructure suited for their requirements now, not in the past.
Quite. But by your own admission, Manchester is now lumbered with a transport system designed when public transport use in the city (and arguably, the city as a whole) was at its nadir, not one which reflects current demands. This wouldn't be a problem if TfGM had the honesty to accept that something different is needed now, and the money to do something about it. But so reluctant are they to admit that they have been lumbered with a second rate transport system, their only solution is to ruin yet more of the heavy rail network by pointless conversion, rather than provide what would actually work best. The parallels with South Wales are obvious.
As for your other points, are you saying that every tunneled metro system in the world except London's is stagnating? If so, why are so many other countries building them? Do we in Britain know something they don't, in our infinite light rail-based wisdom?
The only other lines vaguely comparable to tunneled metro in Britain are Merseyrail, T&W Metro and the Glasgow suburban networks. I don't know about the other two, but Merseyrail doesn't seem to me to be stagnating, and new trains are being procured on the assumption of 40% more passengers by 2028. If Merseyrail is stagnating, might that be something to do with there having been no system expansion in 23 years, and Liverpool's anaemic economic performance since 2008?
Whatever the position, I'm just glad that no-one was around in the early 70s to suggest that Liverpool's heavy rail lines should have been ruined with trams. O often wonder whether the disdain some people express towards Merseyrail stems from the fact that it's completion, at the time the Picc-Vic link was cancelled, was probably the last time a major public spending decision was made in favour of Liverpool rather than Manchester.
As for the notion that Metrolink has played any serious role in Manchester's growth in recent years, I think that might be a bit more down to colossal public and private sector investment, in particular concentration of public sector jobs (Manchester being the only place outside London to have increased public sector employment since 2010). Still, 10 out of 10 for chutzpah.
Your talk of misplaced pride is amusing. Which is worse, taking pride in an expensive system which transports a large number of people quickly and comfortably, or taking pride in a system whose chief attraction is, by your own admission, cheapness, just because It's the only system the short-sighted penny-pinchers who run Britain would pay for?