Most natural gas is not used in power plants, but for heating homes and in all sorts of industrial processes in a lot of cases that is for heating. Shutting down gas power plants is just an easy way of saving gas. In general in the next decade the challenge is less to get the grid 100% clean, but more to connect things to it, with heat pumps, electric cars, new industrial production processes and so forth.

That being said wind and solar are intermittend, but most of the time we have some wind and sunny days are also fairly common. That becomes even more true the larger the grid is. To put it quite simply it is always windy or sunny somewhere in the world, it is just a matter of transporting it. Within the EU that is already happening. Other then that overbuilding renewables is a good strategy as well, for days with some clouds and less strong wind. Those are much more common the perfect days. As for storage periods of no wind or solar are on average fairly short. So most of them can be bridged with fairly small power storage. With a days worth of storage on a nation sized grid, you can in most cases run 95% wind and solar with overgeneration. We even have quite a lot of it with reservoir hydro already. Some of that can even be seasonal.

That being said, last year the EUs electricity grid was 60% low carbon electricity already and that share is rising. So it makes already sense electrify everything possible. Intermittency is a problem, but it is not usolvable and in fact we are already working on a lot of the solutions.