I reckon utopia has been mans' dream and anticipation for ages , he has gone through cycles of yearnings for utopia ensued by feelings of grief, frustration as well as disenchantment with their organizations . This vicious circle has perpetuated itself throughout human life and is still afflicting human mind. Nostalgia is certainly the result of these emotional roller coasters and has proved the massive significance of our past, identities and backgrounds. This feeling of nostalgia has been the legacy of man's disillusionment with an idealistic perfect impeccable society and may be supplanted by dystopic identity.
I think it depends strongly on which nation, country, part of the world or domain that one attempts to answer this from. In physics, the discipline went from strength to strength and I don't really see that it is nostalgic. From the perspective of Great Britain, it didn't exactly start in utopia given that it started with the South African War (1899--1902), which introduced the world to civilian concentration camps and cost about 2 Billion GBP. Then the great war, followed by depression, the second world war, the loss of colonial empire and the gradual loss of influence in the world. For Britain the Utopia was largely over by the beginning of the 20th century and the century was characterized by one crisis after another with a slow slide to irrelevance that was only stabilized somewhat in the 1980s. So no, I don't think this is a valid characterization.