Again, I don't know what you mean by "capitalism", but it's simply not that case that "we can only take actions that benefit individuals in the short term". In the US context, it's certainly true that many companies make many decisions that are driven by short-term profits, but they also make many decisions that are driven by longer timelines (e.g. capital expenditures). I think the same holds true for non-profit entities, including governments (it's a mix of short-term and long-term thinking).

I think a better line of attack is that externalities are poorly accounted for in our current economic system.

It's pretty clear you do understand what they mean by "capitalism", then.

At this point in many countries the institutions of power have been captured by the owners of capital and many of the issues facing modern society are a direct result of this.

People will always act in their best interest and along the interests of their class, and no class is more class conscious than the capital owning class. In the US, this informs policy, which is generally geared at making the capital owning class more money at the expense of everyone else.

I don't see any other reason for us to have such excess and have it all seemingly go to waste. We could solve world hunger right now with our advances in technology and [corporate] central planning but that would never happen under this economic system.