You do realize that every country is already doing what you are suggesting? The point however is that unreliable renewables doesn't cover anything at all reliably, so you need reliable power to cover 100% of demand or you will have regular blackouts. You can achieve that by having enough battery storage to fuel the whole country for months to last the whole winter, or you build reliable power plants like nuclear, coal or gas. We aren't even close to having the battery solution even within decades, so the only alternative are the unrenewable power plants.

And no, betting on a good winter isn't a solution. If those batteries runs out and large swathes of the country blacks out for months during a cold winter many will die. That is not a good solution.