"Cryptocurrency miners could, in theory, buy massive amounts of solar panels with the money they make by mining" is not in any meaningful way a refutation of the criticism that cryptocurrency actually, right now, in the real world, uses an absurd amount of energy and contributes significantly to the greenhouse gases warming our planet.
I did not check this but Michael Saylor claims that over 40% of mining is done using renewable energy. Considering solar power by itself is a good investment last time I checked ( around 13% ROI depending on your local energy price) then that number will probably increase as it just makes business sense to do it.