After the radical developments of the impressionists, they perhaps believed they had solved the problems of artistic creation once and for all. History teaches us that change continues, however.
While it solved many problems in painting, impressionism didn't lend itself to all types of subject. Colours used tended to be muted, and there was a tendency for paintings to lack excitement. These were the challenges that faced the next generation of painters.
Several approaches were tried, but not all have stood the test of time. Seurat for example tried to reintroduce colour using his pointillistic techniques - interesting, but hardly widely applied.
They took the bold step of believing that the 'essence' of the subject was more important than its faithful reproduction. If perspective wasn't quite right, well, so be it. In terms of being a faithful reproduction of the object painted, their paintings clearly fail (as do most paintings since that time).
But the important thing was that the painting evoked the landscape, the object or the person depicted in the mind of the person viewing the painting. And each in their own way, they achieved this goal exceptionally well. This approach also worked even when applied to mundane objects - a chair, a bowl of fruit.
As a result, the works of art themselves also gained interest as objects in themselves. We would probably spend longer looking at Van Gogh's sunflower paintings than we would at a vase of real sunflowers. And how long would we look at the chair in his famous painting, were we to come across the actual chair itself?
In passing, it should be remembered that photography had recently been invented, and those seeking a perfect rendition of their family could achieve it much more easily than ever before.