Base load is not necessary. It was made because you could build certain types of plants really cheap if they're run all the time at the same level. They aren't a requirement, but rather an economic convenience in an old way of doing things.

Renewables with storage are able to match demand more closely than traditional plants ever could. This results in less wasted power. That means we don't have to replace every GWh of traditional generation with a GWh of renewable.

Hydro and geothermal have both had some interesting breakthroughs the last few years. Small scale hydro can get useful amounts of power from smaller rivers than was feasible in the past. There are places to put them we didn't have before.

There's also high voltage DC lines. The longest deployed one is currently in Brazil, and is about 1500 miles. An equivalent run in the US would mean wind farms in Kansas could power New York, or solar in Arizona could power Chicago. When you can transmit that far, then the wind is always blowing somewhere, and it's sunny somewhere for the entire day, as well.

Nuclear lost its window of opportunity. It may already be cost competitive with putting solar panels in space.

Edit: fixing autocorrect's bad corrections