Yechezkel, Rav Sololovetchik and Rav Hutner were certainly giants of their generation, but they only went to university after they had mastered much if not all of shas and poskim.
Trying My Best, indeed, that is a very popular “pro-kollel” argument. However, you must take into consideration that the Rambam is discussing a city, not the overall population of the world. So there are those who will argue that one town where %50 of the population learns all day does not accord with that Rambam. Also, it’s not so pashut it’s a ratio thing.