I am sorry that you were disapointed with your visit.
The largest of the gallery sites is the Trade Fair Palace, which houses the National Gallery's collection of modern art. Other important exhibition spaces are located in the Convent of St Agnes of Bohemia, the Kinský Palace, the Salm Palace, the Schwarzenberg Palace, the Sternberg Palace, and the Wallenstein Riding School. I recomend you to always chceck our website - https://www.ngprague.cz/ to find what suits you the best.
I hope that next time you are going to find some other exhibition in our gallery you would like to see.