Sure, most countries that already made it use hydro. But Denmark is already up tp 80% without hydro, and the UK and Germany are already nearly halfway there without any meaningful hydro. And there’s still so much solar and wind that can still be installed. They’re nowhere near their maximum production capacity yet.
100% from renewables is clearly feasible and achievable. Of course it takes time and investments, but nuclear energy will takre more time and investments to get going again.