It’s weird isn’t it? I can’t think of any other traumatic time which is memorialised with the equivalent of Lindy hop dances, victory rolls, spitfire flybys, dressing kids up as evacuees etc It does feel like we celebrate a war in which millions died and there was a genocide.
Isn't it just that, unlike WWI, the Spanish Flu and the depression, there was a victory, and a reasonably clear end to the whole horrible experience? There were years when the people living through the war didn't know what was going to happen, and then there was relief when it came to an end. The most extremely over-simplified narrative of the war would say there was danger, tragedy, adventure (for some), and then a happy ending. That's why the war featured so heavily in books and films for the decades after it.
Clearly within that there are many many different stories ranging from the tragic to the completely mundane. People had good wars and bad wars. People are having good pandemics and bad pandemics. If vaccinations can keep up with new variants and get worldwide covid rates down, then we might be more likely to look back with nostalgia on whichever aspects of the pandemic were least stressful and most memorable for us personally, because we'll feel it's ended. What the particular things people might feel nostalgic for are will be completely different for different people.
For instance, there'll doubtless be some people who look back with nostalgia on going to work through empty streets during lockdown 1, and on seeing big cities quite different from how they'd ever seen them before. That won't mean they'll be fetishising the pandemic or looking at the whole thing through rose-tinted spectacles. But that isolated experience might well be something they look back on fondly without it summing up the whole pandemic for them.
I think some of the wartime nostalgia does come from having the luxury of looking back at the drama and danger with the knowledge that it's now over, and from the fact that within the whole thing, some experiences were positive. Plus you've got the usual thing of any generation tending to look back fondly on the era when they were children or their parents were young adults, because it's the first era they've personally witnessed slipping from the present into history.