Well, I agree, but life is short. Why learn algebra rather than complex analysis or probability theory or functional analysis or differential geometry or mathematical logic or general relativity or quantum mechanics or any one of dozens of other topics from physics or mathematics that will almost surely seem more interesting and fun to a non-mathematician? (Not to mention non-mathematical topics...)
I agree there are tons of other things that people should study, like basic linguistics, relativity, quantum physics, optics etc. Geometry should be on top of the list, for as Plato said “let no one ignorant of geometry enter”.
But I don’t think time is an issue really, if you just spend an hour or so each evening reading you csn quickly get a basic understanding of lots of topics in not thst many years.
PS I agree about Mac Lane, he's great