> My usual test for a lot of critics of current systems that offer something "far better" with nearly no downside

The current system absolutely depends on fossil fuels, which are not unlimited. Also it brought us into a mass extinction (we are in it, that's a fact), and it is bringing climate change (which will just be a complication on top of the energy crisis when we pass peak production of fossil fuels - pretty soon).

I don't see that as "no downside"; our system is literally about to collapse.