That’s a taking point that wasn’t very true in the 70s and certainly isn’t close to true now, there are endless methods of balancing a renewables grid for constant power involving endless options for continuous generation methods (solar thermal especially) or battery storage (chemical, gravity, etc) and load balancing using at-peek tied industry (especially e-fuel manufacture)

There’s also a lot of stuff like tidal generation which is hugely promising and drastically underfunded, certainly compared to nuclear.