Is there a way to exclude certain prefabs during map creation? For example to generate a map where there is no launch site?

Thanks in advance

Use just wiped.net to filter maps based on monument, and other preferences to find the size and seed you'd like.

A monument is a huge collection of prefabs. An item like a car, or a crate, is also a prefab. You can block individual items with Component Blocker or entity reducer.