The thing you're missing here is timelines. The reason renewables are expensive is because it requires a grid upgrade to make it work, whereas replacing the old coal generators with new ones wouldn't so much. The kicker is though that once that upgrade is done, maintaining it will be very cheap whereas fossil fuels will continue to get more expensive (both sticker price and the cost of dealing with climate change). It's not like installing more fossil fuels halfway through helps either, we can't use coal to eliminate the duck curve without massively overbuilding it for a huge up front cost. We would need to build enough of it to cover when there is no renewables... which would be enough to never use the renewables at all.

There is a lot of evidence in fact that we have _already_ reached the point where just going all in on renewables is cheaper. People like to point to the last 40 years or so to say fossil fuels are cheaper but that was a time when the rate of new power generation wasn't very high and most power stations had already been built. We are at a point now where just about all of our coal power stations need replacing, and actually doing that would be more expensive than the renewables roll-out.

As for nuclear, the average cost to install and run it _in countries with existing industry_ is also higher than renewables. Despite the costs renewables are actually the cheapest method to get power, even if you add in all the extra associated costs.

If you're actually interested in reading up on this then I can suggest going through the GenCost report https://www.csiro.au/en/research/technology-space/energy/Ele...

Of course if you think the CSIRO is full of paid shills then this won't help, but you should probably have a hard think on who is actually spending the most on lobbying money, which you can also look up quite easily.