Sure but is making up good stiff zero effort?
I guess it just goes to show how different different people are, I hold basically the exact opposite view. Remember a few dozen numbers? Sure, no problem. Do some 2 digit mental math? Won't slow down the game at all. Use basic tactics? I'd be doing that anyways.
Come up with an appropriate, compelling consequence for "success at a cost" for roughly half of all die rolls? I'm going to struggle, and the quality of the game will struggle for it.
I could be misrepresenting a conversation I wasn't there for, but the OP made it sound like "Atlas" systems were systems that provide good sessions when run by good GMs and bad sessions when run by inexperienced/bad GMs. If a good GM runs a fast campaign with no pauses, and an inexperienced GM runs a similar campaign with a few 3 minute breaks to do some math or look up a rule, I'd still probably enjoy the second campaign, although likely not quite as mich. If a good GM runs a fun campaign with interesting and appropriate consequences, and an inexperienced GM runs a similar game with boring consequences that don't logically fit the set up, I don't think I would enjoy the second campaign much at all.
It's not about how "easy" or "hard" a system is necessarily, it's about how much the outcome depends on the skill and effort of the GM.
True, there are systems like that. Most systems have some form of a built-in setting though, and those that don't can just use one of the many generic settings that people have published, so it doesn't make as much sense as the criteria for these categories.