Also to end my ‘everyone point and laugh at stupid Communists’ rant the next time you meet one ask them how Marx saw Communism coming about? Answer: he never figured it out. He decided it would be helped along by The Party somehow but not how capitalism would fail or what the superior Collectivist system would look like before he croaked. Result: there is no one standard set for what a successful Communist government is supposed to be BECAUSE NO ONE FINISHED THE FUCKING THEORY BEFORE IMPLEMENTING IT. This has led to hilarious times like the holodomor, the Great Leap Forward, the famines of North Korea, and can’t forget those fun times in glorious Venezuela. So yeah capitalism may not be the best system in the world and I won’t be one to rah rah for it but anyone past a teenager wearing a Che Guevara shirt is a laughable loser.
Marx did that somewhat intentionally, he liked to distinguish himself from 'utopian socialism' which focused on imagining utopian societies and setting forth how they should work. The idea was that the communist's role wasn't to set out the minutiae of a future society, but to allow the future to determine this, although Marx went too far with this. Hence, statements like, "Communism is for us not a state of affairs which is to be established, an ideal to which reality will have to adjust itself." This is quite retarded, as you say, but it is by design. The theory is deliberately 'unfinished,' and actually tries very hard to dissuade anyone from finishing it.
Marx also made dumb comments about the Russian peasant commune forming a way to fast-track Russia into industralised communism, something that obviously was of little practical use to the Bolsheviks.
In terms of the fall of capitalism, Marx did vaguely suggest that it might be due to a crisis caused by a falling rate of profit:
These contradictions, of course, lead to explosions, crises, in which momentary suspension of all labour and annihilation of a great part of the capital violently lead it back to the point where it is enabled [to go on] fully employing its productive powers without committing suicide. Yet, these regularly recurring catastrophes lead to their repetition on a higher scale, and finally to its violent overthrow.
This is still not particularly specific. Marx's vision is slightly Luddite, basically that the increase of technological development and machinery ('constant capital') displaces labour, the creator of value, and therefore leads to an overall economic diminution. This theory is mostly outdated, but most Marxists aren't even aware that it exists, they just think that communism is 'inevitable' because 'the people united can never be defeated' or w/e.
In practice, Marxists generally took power by taking advantage of ongoing wars (Bolsheviks) and independence movements, though such Marxism has stalled somewhat since the collapse of the USSR. Even the tame Paris Commune was a result of a war. Since Marxism is amorphous, obviously people didn't have to care much about the details once they took power. Radicals taking advantage of a war to come to power has little relation to Marx's theory of inevitable social collapse, and there are plenty of examples of such things in the Middle East, Nazi Germany, and elsewhere without much 'Marxism' involved.
Marxism is quite amorphous, but some Marxists will make a lot of fuss about how it's 'classless and stateless,' and everyone owns the means of production in common. Obviously, if 'everyone' owns the means of production, a state or government will be needed to legislate that I can't just go up to a workplace and steal a guy's hammer or wreck machines because I 'own' them. So this kind of definition is barely more specific. In general, Marxism is sort of like a prototype of the modern grifter's ideology, it can mean almost anything to anyone and basically says, 'Have a revolution and put us in power, then we'll find out what we want.' It basically allows them to claim utopian ideals without actually bothering to commit to them, and then blame social problems after their revolution on counter-revolutionary kulaks.
It's a bit strange that Marx's view on communism was so vague, because his long criticism of the "Jewish nigger" Lassalle goes into such detail as to speculate about the minutiae of Lassalle's origins:
It is now quite plain to me — as the shape of his head and the way his hair grows also testify — that he is descended from the negroes who accompanied Moses’ flight from Egypt (unless his mother or paternal grandmother interbred with a nigger). Now, this blend of Jewishness and Germanness, on the one hand, and basic negroid stock, on the other, must inevitably give rise to a peculiar product. The fellow’s importunity is also nigger-like.
(This passage may be somewhat influenced by Marx's interest in phrenology.)
In fact, some of his early writings could also be somewhat pointed:
We recognize in Judaism, therefore, a general anti-social element of the present time, an element which through historical development – to which in this harmful respect the Jews have zealously contributed – has been brought to its present high level, at which it must necessarily begin to disintegrate.
[...]
Judaism could not create a new world; it could only draw the new creations and conditions of the world into the sphere of its activity, because practical need, the rationale of which is self-interest, is passive and does not expand at will, but finds itself enlarged as a result of the continuous development of social conditions.
However, even here he concludes with some vague platitude where the abolition of huckstering and money will abolish the Jewish problem and the influence of egoistic self-interest, and the Russian Revolution is a good enough example of how communist revolution is insufficient to prevent an egoistic Party from taking power into its own hands.