Going out in jamaat

what is the purpose of jamaat, they keep claiming its so that you change, we have people going for 4 months and nothing different with them, no new things or ideas of stuff come out, in every musjid, deen is based on SALAAT, 1 minute madressa lesson after magrib, and tafseer or kitab reading about esha.during Nabi (SAW) time, everything was done from musjid , why is there no emphasis on speading lots of time in your own musjid, ideas have come to mind, exams time make musjid as a study hall, have lots of qiyaamul laa’l, have braais at musjids, have community problems and issues addressed in musjid