>big series are crammed into much smaller mediums all the time.
Well yes but this more of a problem of the medium differences, written can be very verbose describing a scene that will just take a panel on a manga or 10 seconds in anime but then LN pacing is around a volume were even individual chapters can vary in length, the problem that manga and anime face is the ending points since novels can have chapters that when adapted would just not take a whole chapter/episode so ending points became a problem, one way to solve that in manga is simply padding the chapters with more panels or just take more/less pages as anime have a much tougher time as unlike manga, they have very strict lengths.