Which handful, because of the way the system works, are (pretty much by definition) the ones where most qualified and sponsored applicants come from, since the waiting lists are simply the result of the degree to which fully qualified (including sponsored) applicants in the category from the country exceed the by-country limits for the category.
The system doesn't explicitly discriminate against "talented" countries, it just stacks the odds against highly populated countries since there is a per-country cap on the number of GCs issued.
It stacks the odds against countries with a large number of qualified applicants in any category (since the caps are per category.) Population plays a role, but only because it influences representation in the category (which is a big factor for India and China), but so does interest level (which is a big factor for Mexico and the Phillipines, which are particularly impacted for family-based immigration as well as employment-based immigration categories.)