How would you replace “thorough” in the context below? “Insi...

How would you replace “thorough” in the context below?

“Insisting that there was no simple way in which reading and the use of English could be improved, and that improvement required a thorough understanding of the many complexities in language, and action on a broad front, the committee offered 333 conclusions and recommendations; only with reluctance was it prepared to select 17 of these as its principal findings”.