Scotland: A Changing Nation, National Museum of Scotland, Edinburgh

When putting on a new display, the first question curators have to ask themselves is: "What do we want visitors to leave with?" This question, evidently, was never asked for Scotland: A Changing Nation. The display declares what the exhibition is about, but that's not the same thing.

The exhibition "explores some of the major challenges, changes and continuities with the past faced by those living and working in Scotland from the first world war to the present day". So the curators can say anything they want to. But what did they really want to say? One word sums it up: triumphalism.

As you can imagine with a theme this big, it's a quick march. Both world wars are over in five strides. No victims, only winners. A personal panel shows soldier Daniel Laidlaw above the VC he got for playing the pipes to encourage men "over the top" of the trenches during the Battle of Loos in 1915. He survived.

The Great Depression of the 1930s is skipped, although it still haunts Scotland. The story of shipbuilding - in 1900 half the ships afloat in the world were built on the Clyde - is over within another few paces. The whole tragedy of the closures is reduced to two personal panels showing trade-union activist Jimmy Reid and shipbuilder Eric Yarrow cheek by jowl.

There's an interactive here. "Can you build this ship?" it asks. The whole great industry is reduced to chunks of feather-light black polystyrene. No, this interactive is in the wrong section.

A few paces on and there's another personal panel - Laura Campbell, graduate engineer, above her degree certificate and overalls (neatly folded), tells us that ships used to be built lengthways, but now the Type 45, the most powerful destroyer in the navy, is built in transverse blocks. The Scottish shipbuilding industry does have a future, although we won't question the use.

The whole sorry saga of the Ravenscraig steelworks is shrivelled to a wriggle of steel - an actual splash from the last pouring in 1992. But we must hurry on to Silicon Glen.

Another personal panel - Fumi Hirose, managing director of Shin-Etsu Handotai - tells us that deer and rabbits might like the Scottish weather, but he might have to move some production to south-east Asia, where workers are cheaper.

We learn that 40,000 jobs have been lost in the electronic sector since 2001. "Even so," the museum assures the visitors, "there is a lasting base for more development."

The second half of the exhibition is on Daily Life and is supposed to be about people, but again it's about technological advance. The soap drama of single-end living - when large families lived together in one room - is shrunk to a photo of Agnes McLean over a table runner embroidered by her mother.

She's next to Mrs Barden, above designs for her traditional blackhouse on Skye, which was built with all mod cons in 2006. Poverty next to posed poverty? Forget the slums and housing schemes, the hopes and realities that transformed millions of lives in Scotland.

Vague links

It's all about making it… in Scotland. Home entertainment is not what people actually listened to - there's no Elvis, even though he touched down here - only home-grown talent. So, there's the Scottish punk band the Rezillos represented by a PVC jacket (neatly folded), and a Linn turntable, which was way above the budget of most homes.

But just when you thought you were about to get into the swing, you're back to technology again - a hospital bed, with an ultrasound scanner developed in Scotland to detect obstetric problems.

The Voice of the People beckons. Ah, at last some genuine experiences, some lives fully lived. But no. It's politics. A big screen with the usual faces and soundbites. The museum tells us: "Politics changed dramatically in the 20th century."

And goes on to say: "One of the biggest changes came in 1999 when Scotland gained its own parliament." Alex Salmond, leader of the Scottish Nationalist Party, will be delighted. The display implies that independence, not just devolution, is a "settled right".

Huge halibut

When there are any controversial subjects, the museum steps back, although this is when it should step forward. The urgent issue of sustainable energy is reduced to three photos of wind, water and wave power.

The issue of fish stocks is reduced to an interactive that tests your ability to fit a cut-out over an outline of the smallest fish you're now allowed to take. It doesn't show how huge halibut and cod used to grow. The museum might have a view about this - it has a natural history department after all.

The quality of a museum is revealed by what it collects. This museum is still stuck in the 1950s, collecting technological progress. And when it ventures into social history, it does so fatuously. What are you supposed to get out of looking at a boring suit once worn by Gordon Brown?

Museums have to collect resounding evidence, and that now includes films, tapes and discs. If you could hear the tune Daniel Laidlaw played against the sound of shells bursting, or the sound, also heard in 1915, of Mary Barbour's rattle as she called out the women of Govan in the rent strike, instead of seeing them silent at opposite ends of this display, then the meaning of the first world war might begin to come alive.

But this display hasn't begun. Worse, this museum hasn't begun to think.

Julian Spalding is a former director of Glasgow Museums