the funnel-vs-core thing already covered it pretty well so i wont repeat that, but one angle nobody mentioned... small communities give you feedback that followers never will. like actual conversations where people tell you why they didnt buy, what confused them, what they actually want. you cant get that from a follower count.
followers are kinda a vanity number unless theyre doing something. i've seen accounts with huge numbers that move nothing because its all passive scrolling. meanwhile a tight discord or sub where people actually reply to each other does the selling for you, members convince other members way better than you ever could.
that said the "community dies without inflow" point is real. ive watched it happen. people leave, nobody new comes in, and suddenly its a ghost town with 12 active out of 800. so yeah you do need some top of funnel pumping people in, just dont mistake the inflow for the actual asset.
short version, followers find you, community keeps you alive. building for engagement is the better long game imo but treating it as pure either/or is how people end up with a dead server full of lurkers.