Also -- social systems can't be 'replaced' as a worn-out refrigerator or pair of pants. Engineers _know_ the parts & the relations that constitute a refrigerator and can produce a new one to replace the old. No one _knows_ all the 'parts' of _any_ social system, even one's much less complex than capitalism, held together by external relations rather than the complex & only partially known internal relations which constitute capitalism.
A mass movement in one nation might cause the power relations there to collapse, leading to to a constituent assembly generated by local assemblies, but it couldn't create a "new" system at once. It would be very messy. It is going to be a very messy world for quite a while regardless of what happens.
Get rid of such irrational (!) expressions as "replace capitalism."
It has to be overcome for humans to survive as a species, but arguing that it needs "replacement" is a ridiculous way to go about trying to contribute to such an enterprise.
One very small suggestion would be marginally helpful. Those who know that capitalism must be overcome should stop whining about each particular evil as they stumble across it on the web. They could put their brains to better use.
Carrol