Earlier quoted context omitted.
This reminds me of that comment attributed to Bill Gates: "64k memory ought to be enough for everybody" The trend is very clear: solar and wind are dropping in prices. It's now only a matter of when, not if.
They can drop to zero, they are still not going to replace regular power plants because you can't guarantee baseline power with them. You could drop all power generated with them into pumping water to huge reservoirs, so they can generate baseline power around the clock, but it's not feasible in a lot of places, and you are losing a lot of energy just to move the water up and down.
Baseline power is the observation that if we have less than ideal power plants that need to run 24/7 to be economical (usually because of high capital costs, e.g. nuclear plants), we can still deploy them if we then also invest in other plants for filling in the peaks.
See, the important part here is that you always need to meet demand (maybe you can shift demand around a bit, but after shifting it the observation still holds).
If you have baseline plants, your supply curve is a flat line so the peaks in the demand are the holes you need to fill in somehow.
With a renewable source like wind or solar, you may actually be able to meet the peak demand, but then have a hole in the supply at some other point (say at night, or when there's no wind). So you need to fill in these somehow (as you say).