In truth I don't even remember the plot, but I do poignantly remember the evocative language and beautiful prose, even in its English translation. It was just such a subtly piercing way to look inside people in everyday (yes, boring) situations as they struggle with love and meaning. It's the same "big" questions any literary novelist tries to tackle, but if that's not your jam, the writing won't do anything for ya. Nothing wrong with that. Kundera is a niche/cult favorite, not necessarily a mass market page turner.
There are authors I dislike too, despite their popularity. Tolkien and RR Martin for their verbosity, Barbara Kingsolver for her tendency to go on long rambly tangents about her personal life. Thoreau had his ups and downs. Etc. There are more great books and authors than a person can read in a lifetime anyway. To each their own!