what was again the problem with

allprojects

and

subprojects

? They don't play well with the configuration cache or?

Yes, though it's also about configuration on demand and project coupling, see e.g. https://docs.gradle.org/current/userguide/multi_project_configuration_and_execution.html#sec:decoupled_projects and https://docs.gradle.org/current/userguide/sharing_build_logic_between_subprojects.html#sec:convention_plugins_vs_cross_configuration.

ps: the second link is the same

Fixed.

cross-project configuration blocks caused my team so much technical debt in our build because of how tightly coupled all of our subprojects ended up being as a result of years of build neglect. It was a massive effort to hack out and migrate to convention plugins but well worth it!