For the US grid that is very true. There are nations which has reached closer to peak renewable and a good example is Denmark. At peak time wind production is almost 100% and if I remember right they export a lot when that happen, but then we have times like right now (when this comment is posted) and wind production is less than 10% of total usage and both natural gas and coal produce sits above 10% to compensate, in combination with imports from Germany which is also right now mostly produced from coal. (https://www.electricitymap.org/?page=country&solar=false&rem...)
Hydro as a natural resource is not a perfect fit to use in case like this as natural lakes can only take so much changes in water levels, and in many cases you have chains of hydro plants and lakes which mean dumping a lot of water in one place means you have to dump a lot of it further down without causing flooding. Hydro plants must also manage how much water they have available. Swedish power prices is notorious effected by how much water winter/fall periods produce.
Hydro as a natural resource is not a perfect fit to use in case like this as natural lakes can only take so much changes in water levels, and in many cases you have chains of hydro plants and lakes which mean dumping a lot of water in one place means you have to dump a lot of it further down without causing flooding. Hydro plants must also manage how much water they have available. Swedish power prices is notorious effected by how much water winter/fall periods produce.