I disagree. Assumptions made in the video are realistic. You kinda need battery storage for your solar/wind.
Other sources can be hard/impossible to stop.
Batteries are the only form of storage that's scalable. Hydro exist, but you can't expect to just add another hydroelectric dam, whenever your solar overwhelms your current capacity. Hell even storing gravitational energy probably requires frankly massive amounts of development.
You are allowed to import/export electricity, but the assumption is others will have similar power sources, no? When there is the excess sun in one area, it's either going to be excess in nearby areas (because day happens nearby at the same time). Sure, you want to export to countries without sun, but the loses are probably going to be huge (loses mean infrastructure is stressed additionally).
What other renewable resources?
- Hydro? Destructive for the environment kills migrating fish, ruins ecosystems and not available everywhere.
- Geothermal? Only available at a few places can possibly lead to earthquakes.
- Bioenergy? Causes horrible air pollution.