You know that the manifesto is remarkably full of praise for the bourgeoisie, given that it is a communist and thus anti-bourgeois manifesto. Is this praise essentially for capitalism's economic dynamism, the these productive forces that the bourgeois has unleashed? Under communism would liberate those forces at present amissurate, you ask. It's a really excellent way of posing the question. The passage you read is probably not just the most evocative, but to my money, the most beautiful and the most well-known passage in the manifesto.