Improved efficiency of computing hardware.
Increased development of renewable electricity.
Development of geothermal energy in remote /economically disadvantaged areas.
Use of surplus electricity and methane. Use of methane from landfills (and people farts).
On the other hand:
They are still using "lots" of energy.
Still using "lots" of coal and other fossil fuel sources.
Opportunity costs when using surplus sources (could be used else where).
IMO your point is somewhat valid, though "no new business creation" is obviously an exaggeration. Every application of some technology (Bitcoin mining, to mention just one aspect, is highly technological, as are other aspects of putting the equipment somewhere and operating it) involves a very deep supply/maintenance chain, which diffuses investments through society, in part local, in part elsewhere.
I would agree that with Bitcoin mining, there may be less local investment in broader ranges of businesses on average, than with many other kinds of investments. But local development of business/society is a complex topic with many many aspects generating all kinds feedback, so it's IMO very hard to make general and yet truthful statements about this.
There's another aspect that comes to my mind: in a way, letting people invest directly in money creation, as you put it, can be a benefit to the environment. How so? Money being saved instead of being reinvested or spent immediately is effectively people taking their feet off the gas pedal of the economy. As long as the worldwide economy is still > 80 % fossil carbon based (energy wise that is, material wise it might even be more), deceleration should be mostly a benefit for the ecosphere/environment.
The El Salvador (with geothermal power development) program could also be a nice way to fund government and boost local economies.
Using excess power generated by renewables can help fund the development the renewable power sources. In slack power times use the power for mining. It is done already in other industries.
Remember that the mining does not just generate bitcoins but is a way to pay people to maintain the bitcoin network. Instead of banks handling the transaction miners do. Having a functioning monetary system is generally a good thing. Not that we do not have this already but the crypto currency system offer an alternative. Concentrating on the mining is sort of missing the point of crypto currency.
I would not want to argue that all the project are meeting the stated goals. I am sure that lots of the real goals are for some to make a mint. There is plenty of corruption all around and this is not unique to crypto currency. It is not going to solve all the worlds problems but it has its positive points also.
Edit: Will also add that (just like more traditional banking) there are lots of people doing real work to make these things happen.
