“When a system is egalitarian there is no accumulation & nothing to redistribute. Would Parecon address this problem?”
This is actually not the case. Whether a particular country with a particular type of economy decides to invest, or not, and I think that is what you are referring to here, though I am not sure, is partly determined by the type of economy, partly by the country’s state of development, and partly by actual choices people make, more or less freely.
Take the same country, and consider it with a capitalist economy, or with a parecon – and ignore, for the moment, hostility from without (or within). In the former accumulation is literally compelled by the institutions – meaning a very large part of the social product goes to a very small portion of the population, who in turn invest it. In a parecon, what part of the social product is put to investing in changes, new means of production, etc. etc., is a freely made social choice. And there is another difference. In capitalism, the point of the investment will be generating more profits and maintaining the system of profit making, whereas in parecon the point of the investment will be improving people’s lives while maintaining the conditions of classlessness, equity, etc.
The issue you raise of external counries interfering with efforts at progressive much less pareconish change is real, to be sure. But there is no special issue, much less a negative issue, regarding generating investments, other than those mentioned above.