No they aren't. The coal plants are being converted to natural gas. The fossil fuel powered plants MUST be retained to maintain the base load or the grid fails.
I will add a slight change to that.
In many areas, there actually are no kinds of fuel powered generation. And they are powered entirely by renewable energy.
But those areas are now powered by either solar or wind, but by hydro.
Most of the NW USA is powered primarily by hydroelectricity. It is abundant and cheap, and is also the backbone of a lot of local and regional power grids. Then you have the fossil fuels which have popped up as demand has grown, and hydro was not enough anymore.
A good example of this is Idaho, where some 95% of their power is generated by hydro. And there are a grand total of 8 steam turbine generators fueled by "fossil fuels".
Of those 8, 5 of them have been built in the last 25 years. Because the increase in population and power demand had been stressing the power supply that they no longer had a choice.
Oh, and the 3 that were there before? In more remote areas where the hydro available in the region was not enough in extreme weather so they added local ones.
Oh, and there is a single remaining coal plant that is in the process of converting to natural gas. It's actually a sugar plant, built just after WWII. Where the steam plant is actually used as part of the process to boil down and refine sugar beets to make sugar, and the power generated also powers the processing plant itself. And any excess power generated is sold to the grid.
But for some reason, even though "Greenies" love to accept the power that hydro provides as being "renewable", they actually want to see it destroyed in most cases and tell people it should not be used.