The Sun Exchange is a microfinance solution that gives investors an alternative option to park their money if they do choose, instead of (like your linked article) parking it with an emissions intensive company. If there were more options like this, then there would be enough of a market to draw away some of the investors in those companies into financing alternative ways of energy production. After all, you can't prohibit people from wanting a return on their investment! But you can provide alternatives with as little friction as possible.
no amount of capitalism will fix this problem
I agree in part. I would say that no amount of capitalism by itself will fix this problem in an acceptable time frame.
Eventually fossil fuels will be too expensive due to lack of supply (or perhaps by correctly pricing the externalities), and the market by itself will sort them problem, however the time frame is way too disastrous for humans.
Thus, regulations and support for emerging industries is required. We do see instances of this working. Despite the complete dysfunction of the Australian climate and energy policy, companies are responding to the projected economic playing field and either refusing to build or keep open coal power plants or banks refusing to fund them. This is a market and capitalism in action.
The article you linked correctly identifies investors as the solution to changing the energy market. However, the most frictionless way to do this is to offer enticing alternative investments and harness market forces. This way both companies and investors will change their behaviour to 'win', and those that don't will fall away. We can complain that people should be more moral and altruistic, but that won't have any impact beyond making ourselves feel better.
let me butt in here real quick. We have less than 20 years to reverse climate change. There are no market forces that can do it in that amount of time, and I doubt market forces even could fix the problem.
Capital accumulation is the problem. Money makes money. When people focus on short-term accumulation they will end up with more resources and power, that's just what happens when capital compounds. That means the highest rate of profit, regardless of the consequence for humanity, will always win out. If people refuse to fund places like oil companies, those that do will just get an even bigger return on their investment and grow even more powerful. Capital will have the same result regardless of who controls it.
This doesn't even get into how capitalism has to grow to keep even the illusion of stability, meaning it will uselessly use up all of our resources, and that the tendency of the rate of profit to fall and all of that would eventually kill us off anyway