Variable renewable sources can’t power 100% of the grid, but they can easily power 80% of it without any of the normal whatabout problems. Renewables could also power 120% of the grid without problems, interesting variable loads to take up the extra very cheap energy would manifest soon enough.
Claiming exactly 100% is full of problems is true, pedantic, and nowhere close to any reality which would happen.
Of course there will be a mixture of power sources, relax. You can develop a lot of variable renewables before the issues come up.
Europe needs to develop every power source at the same time, distributing resources compromising for risk, several time frames, and cost. This involves a solar/wind heavy mix along with longer term nuclear developments and large scale energy imports from North America.
Nuclear actually is a solution, in the sense that if you implement it, the problem will go away. Renewables are not a solution in the sense that even if you over-implement to an absurd degree, with present technology the problem will sometimes remain.
The people pointing this out are not zealots, they're people with a basic understanding of how electricity works. It's the people who insist against basic physics that renewables can power 100% of the grid that are the zealots, and now we all will pay the price for accommodating their extremism :(