In a nutshell, historical emissions resulted from the action of people who were not us and who didn't know about the impact of their emissions at that time. This makes it complicated to assign responsibility to their descendants, even if we adopt a free-riding based approach.
Gosseries, A. (2014). Nations, Generations and Climate Justice. Global Policy, 5(1), 96-102. https://doi.org/10.1111/1758-5899.12112 (Original work published 2014)