Comment by toyg

When Marx and Engels wrote their books many "western democracies" didn't even exist, so they weren't responsible for any progress made until the end of WWII. Democracies themselves didn't come to be "peacefully": most European kings had to be forcefully deposed one way or another, after they refused substantial reforms for almost 150 years since the French Revolution (in fact, they spent most of the XIX century actually restricting individual freedoms and ramping up censorship powers). Until WWI, there had been almost no progress in many continental countries on universal suffrage, which of course resulted in no progress on all the other subjects you mention. The period between wars was politically very lively but certainly not peaceful nor "within the democratic process": every country had its fair share of events where police or army would indiscriminately shoot at protestors, strikes would get violent, and so on. The political frameworks born from WWII were then characterised, in most Western European countries, by schemes that basically reproduced the Cold War disposition, with a varying degree of direct dependence of local leftist parties from Moscow. The presence of a well-equipped "hard left" made it possible for softer alternatives to thrive: the Overton window was anchored by the Soviet State on one side.

The only country where you can try and talk of a continuous peaceful development is post-Cromwell Britain, which is why this country is still, in many ways, the less socialist of the lot (and getting less so by the day, I could add). Still, the influence of Soviet ideals was so strong even in this land, that there was stuff like the Cambridge Five, something that today is completely unconceivable.

Violent revolutions are not always necessary, but they can (and did) provide inspiration for wider movements.