That’s not the case. While this is complicated stuff due to the statistics involved, it turns out that a large enough collection of widely distributed renewable generation has statistically fairly predictable outputs, and the statistical deviations from expectation get smaller the more distributed renewables you add.
Which means that storage capacity does not need to match generation capacity.
The reason for this is the periods of time when a renewable grid underperforms reduce in both depth and duration as the average renewable percentage goes up, and so the total amount of energy needed in storage decreases. You never have a time when output drops to 0%, and decreasing periods of time when it drops to 20%, 50%, 80% or whatever. And once that period of underperformance passes, it is followed by overperformance, and the storage (whatever it is) can be refilled fairly quickly.