in the main vs generally

in the main and generally both are adverbs.

Word	Noun	Adjective	Verb	Adverb
in the main	No	No	No	Yes
generally	No	No	No	Yes

As adverbs, in the main and generally are synonyms defined as:

Other synonyms of in the main include in general.

in the main (adverb)	generally (adverb)
without distinction of one from others	without regard to specific details or exceptions
for the most part	without distinction of one from others
	usually; as a rule