(sigh...). As ever, internet discussion doesn't do subtleties. According to your tone, I've expressed doubts about the way listed buildings are dealt with, therefore I want to fit plastic window frames to St Paul's Cathedral. Take a deep breath, stop arguing against strawman ideas.
All I'm suggesting is that the basic interests of the people who live there, and reasonable energy conservation standards should take precedence over preservation. E.g. perhaps it should be a right that everyone is entitled to double glazing and some form of wall and loft insulation. Then the listed building officers have to guide and control to ensure that this is done in a sympathetic way, e.g. wooden window frames or a new sealed unit window behind the original. But all based on the principle that houses are for living in, by the people who own them, and making the place look like a pretty museum is nice but should be secondary to some sort of agreed basic habitation standards.
As things stand, you can live in a house that has damp, cold solid walls and single glazing, and you're not allowed to improve this. Yet, if you build an extension onto that very same house then it has to have a certain width of cavity, insulation all round, double or treble glazing and a whole load of other things. It's contradictory and makes no sense.
Buying a listed building is a massive risk to your money and sanity. You have to realise that it's a big deal, and I get the impression that many don't appreciate this and just think it's something to brag about at dinner parties with no downside.