What I wonder is this. Is our lifestyle sustainable, not just environmentally, but financially, long term. Could any system deliver it, left or right, socialist or capitalist . Or is it just a huge Ponzi scam with a can being kicked down the road, that eventually someone somewhere sometime, is going to have to deal with.

Not really, imho. Nothing to do with capitalism vs socialism. Financial cost is simply a proxy for supply and demand of finite resources (broadly, obviously there are various distortions that come into this) and as population continues to increase and expectations of living standards rise, resources become ‘increasingly finite.’ Everyone can’t have everything.

Regarding medical treatment specifically, it is a significant problem for the NHS that many expect cutting edge treatment to be available to them whatever the cost/benefit reality, simply because it does exist.