They cannot move forward because progress and evolution is ultimately based on social and human contact. So socialism won't evolve from islands within capitalism. Yet through out Europe it has been business as usual. No matter what party was in power economic policty remained unchanged In the election in Australia last year a panel of leading economic experts could not see any difference between the Labour party and neo-thatcherite Liberal party on economic policy. The striking thing about parliamentry democracy is its entirely undemocractic character.
Capitalist democracy is merely an exercise in mass disefranchisement.
Evolution is not necessarily a smooth and even process. The modern veiw of evolution in biology is a story of long periods of stability with little change separated by brief crisis periods. Within this short periods of evolutionary time there were huge waves of evolutionary change along with mass extinctions. During this time hundreds of species perished and hundreds of new ones evolved. It is to the idea of materialism that we turn to for our veiw of how societies evolve.