This is not true. Western Hunter Gatherers preceded Neolithic farmers from Anatolia and their genes survive in the modern populations of Europe.
However it’s hypothesized that during the neolithic farmers immigrating from Anatolia/etc. lived alongside the hunter gatherer communities for quite a while. The types of environments preferred by hunter gatherers didn’t have the soil suitable for early agriculture.
But there probably was still quite a but of friction and violence. Also both groups were very different phenotypically, Western Europeans had very dark/black skin and often blue eyes while the middle eastern immigrants had pale skin and dark eyes.
if we share 98% of our DNA with chimps from a million years ago, what does it mean to say that none of some older DNA seems to have survived?
Albeit there was some mixing even in the areas settled by Anatolian farmers. According to current estimates the WHG population was very low to begin with and they continued living alongside farmers for quite a while (due to both groups preferring different environments/soil types) so it probably was more gradual rather than direct replacement/genocide.