There are several different ways. Demand response is significant. Large users are already paid to reduce their usage during times of tight supply. It should be economical at some level to push that much further down the list. Some utilities today already do time-of-day pricing, so make it much more explicit and allow many more people to participate. The idea that we must allow anyone to use as much electricity as they want at any time is ridiculous.
For seasonal and time of day issues, the intermittency issue is mitigated by the fact that different technologies are strong at different times. Wind is most active at night. So the answer to "what do you do when the sun isn't shining" is in fact "install wind". Similarly, wind is weak in summer. Guess what? Summer has the longest daylight periods. So solar panels produce electricity for many more hours per day. "Use electricity during the day and use much less at night" is a reasonable solution. Again, the bullshit idea that we need to allow everyone to use all of the electricity that they want at any time needs to go die in a fire.