From the article:

This work is an attempt to capture the “whole system costs” of an individual power plant. This could include the costs of enhancing the electricity network to connect a new power station, balancing supply and demand in real time, and providing backup power during periods of low wind or sun.

From the comment I'm replying to:

I wish proponents renewables were honest enough to not withhold these problems

As the article makes clear, nobody is hiding from the fact that there are costs associated with providing backup power during periods of low wind or sun.

The other problems in the comment are not problems with renewables per se (aside from one problem with the straw man "100% renewables"), but problems with German government policy.