Let's See If Taking It one Item At a Time Will be Simple Enough For You
In Situ: Gas phase reactions are easy. CO2 to Methane is old proven technology. So is dust filtration. This is far more feasible than harvesting trace ice fron lunar rock. You are throwing up road blocks that are nonsense to people who have actually bothered to study the topic. NASA adopted this idea because it is highly feasible. I doubt very much your criticism of this issue has anything to do with actual technical constraints but rather your oft demonstrated tendency to badmouth anything to do with exploring Mars whether you know anything about it or not.
Regards,
Mark